CR-positive Cells Research Articles

Deficits of olfactory interneurons in polysialyltransferase- and NCAM-deficient mice.

The neurogenic niche of the anterior subventricular zone (SVZ) persistently generates neuroblasts, which migrate along the rostral migratory stream (RMS) into the olfactory bulb (OB), where they differentiate into granule and periglomerular cells. Loss of the neural cell adhesion molecule NCAM or its post-translational modification polysialic acid (polySia) impairs migration causing accumulations of cells in the proximal RMS and decreased OB volume. Polysialylation of NCAM is implemented by two polysialyltransferases, ST8SIA2 and ST8SIA4, with overlapping functions. Here, we used mice with Ncam1 and polysialyltransferase deletions to analyze how partial or complete loss of polySia synthesis or a combined loss of polySia and NCAM affects the RMS and the interneuron composition in the OB. Numerous calretinin (CR)-positive cells were detected dispersed around the RMS in Ncam1 knockout, St8sia2, St8sia4 double-knockout, and St8sia2, St8sia4, Ncam1 triple-knockout mice, as well as in St8sia2(-/-) but not in St8sia4(-/-) mice. These changes were not reflected by reductions of CR-positive cells in the granule or glomerular layer of the OB. Instead, calbindin-positive periglomerular interneurons were strongly reduced in all polySia-NCAM negative mice and slightly attenuated in St8sia2(-/-) as well as in the St8sia4(-/-) mice, which were devoid of ectopic CR-positive cells along the RMS. Consistent with the early developmental generation of calbindin- as compared with CR-positive OB interneurons, this phenotype was fully developed at postnatal day 5. Together, these results demonstrate that the early development of calbindin-positive periglomerular interneurons depends on the presentation of polySia on NCAM and requires the activity of both polysialyltransferases.

Effects of monosodium glutamate treatment on calretinin-immunoreactive neurons in hippocampus of postnatal rats.

Calretinin (CR) is a protein, which is present in GABAergic neurons and belongs to the calcium-binding proteins family. It may reduce the excitotoxicity phenomenon through its Ca2+ buffering properties. This phenomenon is due to the increase of calcium ions levels caused by the excess of glutamate—the main excitatory neurotransmitter. The aim of the study was to investigate alterations of calretinin-immunoreactivity in neurons of hippocampal CA1 region and dentate gyrus with hilus in 10 day-old rats treated with monosodium glutamate (MSG). Ten 7 day-old Wistar rats were used. The MSG-group consisted of 5 MSG-treated rats at a dose of 4 g/kg b.w. for 3 consecutive days and the second group consisted of 5 control animals. After euthanasia the brains containing hippocampus were dissected and embedded in paraffin blocks. The immunohistochemical peroxidase-antiperoxydase reaction was performed on tissue sections. The morphometric analyses of CR-immunopositive neurons: density, percentage ratio to the density of all cells and an assessment of digital immunostaining intensity were performed. The distribution of the CR-immunoreactive neurons in the hippocampus was irregular. In the MSG-group there were single cells, which were more intensely stained than in control animals. Some of cells contained processes of different length. The density of CR-immunopositive cells and their percentage ratio to the density of all cells did not change significantly after MSG treatment. However, there was a statistically significant increase in the staining intensity of CR-immunopositive cells. The obtained results indicate that CR-positive cells in P7-P10 rats are only slightly affected by MSG in CA1 region and dentate gyrus with hilus of the hippocampus.

Enteric plexuses of two choline-acetyltransferase transgenic mouse lines: chemical neuroanatomy of the fluorescent protein-expressing nerve cells.

We studied cholinergic circuit elements in the enteric nervous system (ENS) of two distinct transgenic mouse lines in which fluorescent protein expression was driven by the choline-acetyltransferase (ChAT) promoter. In the first mouse line, green fluorescent protein was fused to the tau gene. This construct allowed the visualization of the fiber tracts and ganglia, however the nerve cells were poorly resolved. In the second mouse line (ChATcre-YFP), CRE/loxP recombination yielded cytosolic expression of yellow fluorescent protein (YFP). In these preparations the morphology of enteric neurons could be well studied. We also determined the neurochemical identity of ENS neurons in muscular and submucous layers using antibodies against YFP, calretinin (CALR), calbindin (CALB), and vasoactive intestinal peptide (VIP). Confocal microscopic imaging was used to visualize fluorescently-conjugated secondary antibodies. In ChATcre-YFP preparations, YFP was readily apparent in somatodendritic regions of ENS neurons. In the myenteric plexus, YFP/CALR/VIP staining revealed that 34% of cholinergic cells co-labeled with CALR. Few single-stained CR-positive cells were observed. Neither YFP nor CALR co-localized with VIP. In GFP/CALB/CALR staining, all co-localization combinations were represented. In the submucosal plexus, YFP/CALR/VIP staining revealed discrete neuronal populations. However, in separate preparations, double labeling was observed for YFP/CALR and CALR/VIP. In YFP/CALR/CALB staining, all combinations of double staining and triple labeling were verified. In conclusion, the neurochemical coding of ENS neurons in these mouse lines is consistent with many observations in non-transgenic animals. Thus, they provide useful tools for physiological and pharmacological studies on distinct neurochemical subtypes of ENS neurons.

The vulnerability of calretinin-containing hippocampal interneurons to temporal lobe epilepsy

This review focuses on the vulnerability of a special interneuron type—the calretinin (CR)-containing interneurons—in temporal lobe epilepsy (TLE). CR is a calcium-binding protein expressed mainly by GABAergic interneurons in the hippocampus. Despite their morphological heterogeneity, CR-containing interneurons form a distinct subpopulation of inhibitory cells, innervating other interneurons in rodents and to some extent principal cells in the human. Their dendrites are strongly connected by zona adherentiae and presumably by gap junctions both in rats and humans. CR-containing interneurons are suggested to play a key role in the hippocampal inhibitory network, since they can effectively synchronize dendritic inhibitory interneurons. The sensitivity of CR-expressing interneurons to epilepsy was discussed in several reports, both in animal models and in humans. In the sclerotic hippocampus the density of CR-immunopositive cells is decreased significantly. In the non-sclerotic hippocampus, the CR-containing interneurons are preserved, but their dendritic tree is varicose, segmented, and zona-adherentia-type contacts can be less frequently observed among dendrites. Therefore, the dendritic inhibition of pyramidal cells may be less effective in TLE. This can be partially explained by the impairment of the CR-containing interneuron ensemble in the epileptic hippocampus, which may result in an asynchronous and thus less effective dendritic inhibition of the principal cells. This phenomenon, together with the sprouting of excitatory pathway axons and enhanced innervation of principal cells, may be involved in seizure generation. Preventing the loss of CR-positive cells and preserving the integrity of CR-positive dendrite gap junctions may have antiepileptic effects, maintaining proper inhibitory function and helping to protect principal cells in epilepsy.

Seizures during pregnancy modify the development of hippocampal interneurons of the offspring

We investigated the effect of epileptic seizures during pregnancy on hippocampal expression of calcium-binding proteins in the offspring. Female Wistar rats were submitted to the pilocarpine model and mated during the chronic period. Seizure frequency was monitored over the entire pregnancy. Pups were perfused at postnatal days 6 and 13, and the brains processed for Nissl staining and immunohistochemistry for NeuN, calbindin, calretinin, and parvalbumin. Number of stained cells in the hippocampus was estimated through stereological methods. Our results showed a decrease in epileptic seizure frequency during pregnancy. No differences were observed in NeuN-positive, CR-positive cells, and Nissl-stained hippocampal neurons between the groups. However, there was a significant decrease in calbindin-positive cells ( P = 0.005) and a significant increase in parvalbumin-positive cells ( P = 0.02) in the experimental group when compared with the control group. These results suggest that seizures during pregnancy affect the development of specific hippocampal interneurons of the offspring.

Comparative analysis of calbindin D-28K and calretinin in the retina of anuran and urodele amphibians: Colocalization with choline acetyltransferase and tyrosine hydroxylase

Previous studies in amphibians yielded contradictory results about the distribution of calbindin-D28k (CB) and calretinin (CR) in retinal neurons, most likely due to the different antibodies used. The present comparative study aimed to characterize the distribution of CB and CR in relation to retinal neurons in six species of anuran and urodele amphibians by using the same immunohistochemical protocol with specific poly- and monoclonal antibodies. CB was specifically found in cones, in subpopulations of bipolar and amacrine cells and in sparse neurons in the ganglion cell layer. All photoreceptors were negative for CR, whereas subpopulations of horizontal, bipolar and amacrine cells as well as cells in the ganglion cell layer contained CR. CB/CR colocalization occurred in some amacrine cells and in cells of the ganglion cell layer, with variable proportions among species. Most of the ganglion cells identified by retrograde labeling from the optic nerve contained CB and/or CR. Cholinergic cells, visualized by choline acetyltransferase (ChAT) immunoreactivity, constituted a subpopulation of the CR-positive amacrine cells in anurans and a high percentage (40-90%) of cholinergic cells were CR immunoreactive in urodeles. CB/ChAT colocalization was between 10 and 30% in anurans and lower in urodeles (7-10%). Finally, CB colocalized in 6-8% of the tyrosine hydroxylase (TH) amacrine cells only in anurans, whereas CR and TH colocalized in 5% of TH cells in the urodele retina. Our data suggest a specific pattern for CB and CR distribution in the retinal neurons of amphibians comparable to amniotes in some cell types showing, however, peculiar features not observed previously in other vertebrates.

Estrogen receptor β is essential for sprouting of nociceptive primary afferents and for morphogenesis and maintenance of the dorsal horn interneurons

Estrogen is known to influence pain, but the specific roles of the two estrogen receptors (ERs) in the spinal cord are unknown. In the present study, we have examined the expression of ERalpha and ERbeta in the spinal cord and have looked for defects in pain pathways in ERbeta knockout (ERbeta(-/-)) mice. In the spinal cords of 10-month-old WT mice, ERbeta-positive cells were localized in lamina II, whereas ERalpha-positive cells were mainly localized in lamina I. In ERbeta(-/-) mice, there were higher levels of calcitonin gene-regulated peptide and substance P in spinal cord dorsal horn and isolectin B4 in the dorsal root ganglion. In the superficial layers of the spinal cord, there was a decrease in the number of calretinin (CR)-positive neurons, and in the outer layer II, there was a loss of calbindin-positive interneurons. During embryogenesis, ERbeta was first detectable in the spinal cord at embryonic day 13.5 (E13.5), and ERalpha was first detectable at E15.5. During middle and later embryonic stages, ERbeta was abundantly expressed in the superficial layers of the dorsal horn. ERalpha was also expressed in the dorsal horn but was limited to fewer neurons. Double staining for ERbeta and CR showed that, in the superficial dorsal horn of WT neonates [postnatal day 0 (P0)], most CR neurons also expressed ERbeta. At this stage, few CR-positive cells were detected in the dorsal horn of ERbeta(-/-) mice. Taken together, these findings suggest that, early in embryogenesis, ERbeta is involved in dorsal horn morphogenesis and in sensory afferent fiber projections to the dorsal horn and that ERbeta is essential for survival of dorsal horn interneurons throughout life.

Calbindin-D28k and calretinin immunoreactivity in the spinal cord of the lizard Gekko gecko: Colocalization with choline acetyltransferase and nitric oxide synthase

The distribution of the calcium-binding proteins calbindin-D28k (CB) and calretinin (CR) was investigated in the spinal cord of the lizard Gekko gecko, by means of immunohistochemical techniques. Abundant cell bodies and fibers immunoreactive for either CB or CR were widely distributed throughout the spinal cord. Most neurons and fibers were labeled in the superficial dorsal horn, but numerous cells were also located in the intermediate gray and ventral horn. Distinct CB- and CR-containing cell populations were observed, although double immunohistochemistry revealed that 17–20% of the single-labeled cells for CB or CR in the dorsal horn contained both proteins. In addition, nitric oxide synthase was immunodetected in about 6% of the CB-positive neurons in the dorsal horn and in 10% in the ventral horn, whereas nitric oxide synthase was present in 9–13% of CR-positive cells in the dorsal horn and in 14% in the ventral horn. These doubly immunoreactive cells were restricted to areas IV, VII and VIII. Similar colocalization experiments revealed that 18–24% of the cholinergic cells in the ventral horn contained CB and 21–30% CR, with some variations throughout the length of the spinal cord. The pattern of distribution for CB and CR immunoreactivity in the spinal cord of the lizard, reported in the present study, is largely comparable to those reported for mammals, birds and anuran amphibians suggesting a high degree of conservation of the spinal systems modulated by these calcium-binding proteins.

Mouse cortical inhibitory neuron type that coexpresses somatostatin and calretinin

Mammalian cortex contains a diversity of inhibitory neuron types, each with distinct morphological, immunochemical, and/or physiological properties. In rat cortex, chemical markers distinguish at least four distinct and nonoverlapping neuron classes based on expression of parvalbumin (PV), somatostatin (SST), calretinin (CR), and cholecystokinin (CCK). It has generally been assumed that these classifications should also apply to other rodent species. In mouse cortex, however, we found significant colocalization of SST and CR in inhibitory neurons; about 30% of SST-positive cells contained CR, and about 33% of CR-positive cells contained SST across frontal, somatosensory (S1), and visual cortex (V1). The SST and CR colocalized cells were concentrated in layer 2/3. We further characterized morphological and physiological properties of the mouse cortical inhibitory neuron types that express SST by using "GIN" transgenic mice, in which GFP is expressed in a subset of SST inhibitory neurons (see Oliva et al. [2000] J Neurosci 20:3354-3368). Generally, both SST/CR+ cells and SST/CR- cells exhibited morphological features of Martinotti cells as described in rat cortex, and they also had similar accommodating spike-firing patterns. However, they differed significantly in quantitative comparisons of morphology and spike shapes. SST/CR+ cells had more horizontally extended dendritic fields and more primary process than did SST/CR- cells; and SST/CR- cells had narrower action potential widths and faster afterhyperpolarization than did SST/CR+ cells. Thus, our data show an important species difference in the chemical distinction of inhibitory neuron subtypes, and indicate that colocalization of CR in SST cells correlates with different morphological and physiological features.

IgG and complement receptor expression in children treated by peritoneal dialysis

Children treated by peritoneal dialysis (PD) are at increased risk of infections. IgG receptors (FcgammaRs) and complement receptors (CRs) on white blood cells (WBCs) are important for the phagocytic process. We have investigated FcgammaR and CR expression on monocytes, macrophages and neutrophils in blood and in peritoneal dialysis effluent (PDE) of 39 PD children. WBCs were isolated from blood and PDE, labelled with FITC-conjugated CD16 (FcgammaRIII), CD32 (FcgammaRII), CD64 (FcgammaRI), CD11b (CR3) and CD35 (CR1) monoclonal antibodies, and analysed by flow cytometry. Peritoneal cells had lower percentages of FcgammaR-positive or CR-positive cells than blood. On the other hand, the receptor number per cell [mean fluorescence intensity (MFI)] was higher on peritoneal macrophages and neutrophils than blood, except for CD16. The FcgammaR and CR expression in blood and dialysate did not change significantly during the first year of PD treatment. During a peritonitis episode the MFI of all receptors in blood increased only on monocytes, with the exception of CD32. The percentages of FcgammaR-positive and CR-positive macrophages and neutrophils in the PDE increased, whereas the MFI did not increase consistently. Peritoneal cells of PD children showed a lower percentage of FcgammaR-positive and CR-positive neutrophils and macrophages, combined with an increased MFI, indicating a state of activation. Blood and peritoneal cells are capable of up-regulating the receptor expression during peritonitis but probably not to a maximum level.

Calcium binding protein markers of GABA deficits in schizophrenia--postmortem studies and animal models.

As quantitative neuroimaging continues to elucidate the gross neuropathology of schizophrenia, neurochemical and histological studies have contributed to defining this pathology in terms of neurotransmitter dysfunction. Increasingly, there is evidence implicating neurons containing the major inhibitory neurotransmitter of the brain--gamma-aminobutyric acid (GABA). Benes was the first to demonstrate deficits in some morphological subtypes of interneurons in the frontal cortex in schizophrenia. We identified that this was specific to a subgroup of GABAergic interneurons containing parvalbumin (PV), which is found in the fast-firing cells providing inhibitory control of the cortico-fugal pyramidal cells. PV is notable in being expressed late in development; the late expression of this protective calcium binding protein (CBP) may impart an early vulnerability to these neurons, indicating a possible mechanism for the developmental origins of schizophrenia. Cortical GABAergic neurons expressing the CBP calretinin (CR) are unaffected in schizophrenia, although those containing calbindin (CB) are also diminished in number. These deficits in PV and CB are notable in also being observed in bipolar disorder, indicating how the close aetiological relationship of these two psychiatric disorders is reflected in their pathology. One of the most substantial abnormalities seen in post-mortem brain tissue is the hippocampal deficit of PV-containing neurons, again in the absence of effects on CR-positive cells. This deficit occurring in a structure implicated in cognitive symptomatology may well have functional relevance, and we find it can be induced by a model of the disease, sub-chronic phencyclidine (PCP) administration, that can also produce cognitive disturbances. This PCP model, like schizophrenia, demonstrates other neurochemical changes which include indicators of glutamatergic dysfunction. The temporal and aetiological relationships between glutamatergic and GABAergic deficits remains unclear, but may well relate to an initial loss/dysfunction of GABA/PV neurons that subsequently gives rise to a glutamatergic pathology.

Differential effects of aging on the distribution of calcium-binding proteins in a pretectal nucleus of the chicken brain

The nucleus pretectalis (PT) of birds is an ovoid-shaped visuomotor cell group of the pretectum that receives tectal input and projects back to the optic tectum. We performed immunohistochemical single- and double-labeling to determine the distribution and abundance of neurons containing three calcium-binding proteins, parvalbumin (PV), calretinin (CR), and calbindin (CB), in the PT in chickens at three ages. We found that PV-positive and CR-positive cells co-localize and are largely found in the outer part of PT at all ages. The GluR4 subunit of the AMPA-type glutamate receptor was selectively localized to these neurons. CB-positive neurons, however, were largely absent from the PT in young and adult chickens. The abundance of PV-positive and CR-positive neurons in PT in old birds was indistinguishable from that in the younger birds, but CB-positive perikarya were 10–20-fold more common than in young birds, and were again mainly found in the outer part of PT. The overall abundance of neurons in PT was reduced to about 50% of its former abundance in the old birds, with this loss restricted to the central part of the nucleus. These data indicate that a cell loss process develops in PT as birds age, that parvalbuminergic and calretinergic neurons resist this process, and that this process is associated with increased expression of CB.

Transient calretinin expression defines early postmitotic step of neuronal differentiation in adult hippocampal neurogenesis of mice

We here show that the early postmitotic stage of granule cell development during adult hippocampal neurogenesis is characterized by the transient expression of calretinin (CR). CR expression was detected as early as 1 day after labeling dividing cells with bromodeoxyuridine (BrdU), but not before. Staining for Ki-67 confirmed that no CR-expressing cells were in cell cycle. Early after BrdU, CR colocalized with immature neuronal marker doublecortin; and later with persisting neuronal marker NeuN. BrdU/CR-labeled cells were negative for GABA and GABAA1 receptor, but early on expressed granule cell marker Prox-1. After 6 weeks, no new neurons expressed CR, but all contained calbindin. Stimuli inducing adult neurogenesis have limited (enriched environment), strong (voluntary wheel running), and very strong effects on cell proliferation (kainate-induced seizures). In these models the induction of cell proliferation was paralleled by an increase of CR-positive cells, indicating the stimulus-dependent progression from cell division to a postmitotic stage.

Complement receptors in HIV infection.

Similar to other pathogens, HIV can directly activate the complement pathway even in the absence of antibodies. During and after seroconversion, HIV-specific antibodies enhance the activation of complement and increase deposition of complement fragments on virions dramatically. However, even in the presence of HIV-specific antibodies, no or only poor lysis occurs. HIV has adapted different protection mechanisms to keep complement activation under the threshold necessary to induce virolysis. In addition to its own envelope proteins, the viral envelope contains membrane-anchored host molecules. Among those are complement regulatory proteins that remain functionally active on the surface of HIV and turn down the complement cascade. In addition, serum proteins with complement regulatory activities become secondarily attached onto the virus, thereby enhancing the protection of HIV against complement-mediated damage. Therefore, opsonised virions accumulate in HIV-infected individuals, which subsequently interact with complement receptor (CR) expressing cells. This review is mainly focused on these interactions, which result either in infection of CR-positive cells with high efficiency, or retention of viral particles on their surface via CRs, thereby promoting transmission of virus to other permissive cells.

Calretinin immunoreactivity in pineal gland of different mammals including man.

Calretinin (CR) is a calcium-binding protein, found in a variety of organs and systems such as the central nervous system and the pineal gland. It was first thought to be a specific neuronal marker but this selectivity is now in question since CR has been demonstrated in avian thymus, rat ovary, rat and guinea pig inner ear, rat testis, and chicken and rat pineal gland. To contribute to the knowledge of the presence of CR-positive cells in the pineal parenchyma of rat and other mammalian including man, we performed immunocytochemistry on pineal glands of gerbils, rats, goats, cows, and humans, using a CR anti-serum. To confirm it was actually CR that was demonstrated, we performed Western Blot analyses. Finally, to precisely identify the nature of CR-positive cells we accomplished double-labelling immunofluorescence, using antisera against some nerve cell specific cytosquelettal proteins such as MAP-5, MAP-2, NF-L, NF-M, and NF-H. CR-positive cells were found in all pineal glands studied. These cells all possess a round, oval, or polygonal-shaped perikaryon sending one or more processes of different lengths into the glandular parenchyma. There is a lack of CR immunoreactivity in the nucleus and cell organelles while the cytosol contains a high concentration of this protein. Nevertheless, there are some slight differences between species, especially concerning the number of reactive cells and their relationships with different parenchymal structures such as blood vessels or acervuli. Among the CR-positive cells, only a few were actually nerve cells, contributing probably to an intrinsic innervation of the gland. The remaining CR-reactive cells seem to correspond mostly to pinealocytes in a specific histophysiological state and possibly to neuron-like cells. The significance of the CR-positive cells in the pineal glands remains to be elucidated.

Regional and cellular expression sites of the α 1 subunit of GABA A receptors in the rat basal forebrain: a cytochemical study with glutamic acid decarboxylase, choline acetyltransferase, calcium-binding proteins and nitric oxide synthase as second markers

Forebrain sections of adult male Wistar rats were processed for the immunohitochemical detection of the GABA A receptor α 1 subunit. Alternate sections were used for double-stainingwith antibodies to glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), the calcium binding proteins parvalbumin (PARV), calbindin (CALB) and calretinin (CR) as well as to nitric oxide synthase (NOS). α 1 subunit-immunostained neurons occupied the central part of the medial septum and diagonal band, the whole ventral pallidum and the globus pallidus. A moderate number was found in the lateral septum, and only very few in the striatum and nucleus accumbens. Double-immunofluorescence labelling revealed an apparently complete co-expression of GAD-immunoreactivity in α 1 subunit-immunoreactive cells of rat basal forebrain, but only a region-dependent proportion of GAD-immunoreactive cells showed Co-expression of PARV-immunoreactivity characterized the vast majority of the α 1 subunit-immunoreactive cells in the medial septum, diagonal band, ventral pallidum and globus pallidus. Striatal α 1 subunit-immunopositive neurons appeared PARV-immunonegative and did also not react with the other immunoreagents used in this study, except the GAD-antibody. CR-immunoreactivity was co-expressed in α 1 subunit-immunopositive cells of the ventraal lateral septal nucleus and only exceptionally in the ventral pallidum, where the vast majority of CR-positive cells was monolabelled. A small minority of ChAT-immunoreactive, but in no case CALB- and NOS-immunoreactive cells were found to express the α 1 subunit-immunoreactivity. These findings confirm the data obtained by analyses of other brain regions suggesting a preferred co-existence of this GABA A receptor subunit with PARV and to a lesser degree with CR.

Calretinin-immunoreactive neurons in the trigeminal and dorsal root ganglia of the rat

The cell body size of primary neurons were measured in the trigeminal (TG) and lumbar dorsal root ganglia (DRG) monochrome-stained for calretinin (CR)-like immunoreactivity. A trichrome stain for CR, carbonic anhydrase (CA) and tachykinin (TK) was also employed to estimate possible overlap of cellular distribution of these substances. In the DRG, the cell size spectrum of CR-positive cells was clearly bimodal; a greater proportion (84.1%) of CR-positive cells was distributed in the range ≧ 800 μm 2 with a mode between 1,500–1,600 μm 2, while a smaller proportion (14.8%) < 700 μm 2 with a mode of 400–500 μm 2. They were evenly distributed throughout the DRG. Although CR-positive TG neurons were smaller than similar DRG neurons, a bimodal distribution pattern remained unchanged. 94.6% of CR-positive cells measured 100–1,400 μm 2 with peak ranges of 200–300 μm 2 and 400–500 μm 2. Most of CR-positive cells in the ophthalmic division were 400 μm 2 or larger and small CR-positive cells ( < 400 μm 2 ) were concentrated in the maxillary and mandibular divisions. Most of CR-positive DRG cells showed CA activity (76.5%), while those with TK-immunoreactivity were rare (7.2%). In the TG, 38.4% of CR-positive cells were TK-positive. They were mostly smaller than 800 μm 2. On the other hand, CA was detected in 43.4% of CR-positive TG cells. Most of the TG cells co-expressing CR and CA were 400 μm 2 or larger. Simultaneous co-expression of TK and CA by the CR-positive cells was negligible. The cell bodies co-expressing CR and TK were more or less concentrated in the maxillary and mandibular divisions of the TG. The results suggest that CR-positive DRG cells are mostly proprioceptive, whereas similar TG cells include many small primary neurons innervating the visceral mucosa.

Complement and antibody mediate enhancement of HIV infection by increasing virus binding and provirus formation

Previous studies have shown that infection of complement receptor (CR2)-bearing cells with HIV pretreated with antibody (Ab) plus complement (C) resulted in increased virus expression. The current study was designed to determine whether C-mediated 'enhancement' of HIV-1 production was the result of increased virus infection of cells as assessed by provirus formation and virus binding. Virus was incubated with anti-HIV Ab and/or C and added to CR2-positive MT-2 cells. Increased virus expression by MT-2 cells correlated with increased numbers of HIV-immunofluorescent-positive cells at 24 and 48 h and higher levels of provirus detected 8-28 h after infection. MT-2 cells also bound threefold more Ab-plus-C-treated virus than untreated virus. Serial dilutions of C showed that high levels of C with Ab did not enhance but rather suppressed virus expression. Studies were also performed which showed that terminal C components C5 and C8 were not necessary for the enhancing effect. The increased binding of C-coated HIV to CR-positive cells has important implications for the fate of virus in vivo.

IgG-Fc and C3 receptors in the chicken: distribution, tissue localization and functional significance

This paper summarizes data obtained in our laboratory on the demonstration of receptors for IgG-Fc (FcR) and complement (CR) on mononuclear cells of the fowl. A clearcut distinction of these two structures on spleen cells was achieved in rosette assays using SRBC coated with rabbit IgG as indicator cells which bind avian complement, but are not bound by the FcR. The tissue distribution and localization of FcR and CR positive cells was studied in mixed hemadsorption assays on sections of both central (bursa, thymus) and peripheral (spleen) lymphoid organs from normal chickens, as well as lymphocytic infiltrated thyroid glands from animals of the Obese strain (OS) afflicted with spontaneous autoimmune thyroiditis. The possible significance of both receptors in the pathogenesis of this autoimmune process is discussed.

Tissue localization of lymphocyte surface antigens and receptors for immunoglobulin G Fc and complement in the chicken.

Frozen sections of chicken lymphoid organs were examined for lymphocyte surface antigens by antisera to T and B lymphocytes (ATS;ABS), and for the presence of immunoglobulin (Ig) G Fc and complement receptors (FcR;CR) by hemadsorption with sheep erythrocytes (E) coated with chicken IgG(EA), and E coated with rabbit IgG and chicken complement (EAC). In the spleen FcR positive cells were confined to the periellipsoidal sheaths and the germinal centers. CR positive cells were found in the same spleen areas, as well as in the medulla of bursal follicles. These lymphoid areas reacted strongly with ABS, but they also stained with neutral alpha-naphthyl butyrate esterase, and phagocytosed carbon particles were found in the periellipsoidal sheaths. Furthermore, in vivo treatment with cyclophosphamide, which resulted in pronounced B-lymphocyte depletion, did not affect FcR activity, but reduced CR activity significantly. These data indicate that the FcR activity demonstrated in tissue sections is mainly confined to mononuclear phagocytes, while the CR positive cells are mainly B lymphocytes.