Reciprocal Transfer Experiments Research Articles

Unidirectional IgG allotype- and isotype-specific suppressor cells in congeneic mice

By the use of allotypic markers on immunoglobulin molecules of isotypes IgG1 and IgG2a, in transfers of spleen cells between Igh haplotype congeneic partner strains BALB/c (Igh a) and CB20 (=BALB/c-Igh b), the expression of donor and recipient lymphocytes could be followed differentially. BALB/c donor's allotype a was produced in nonirradiated CB20 recipients for months. By contrast, CB20 donor's allotype b disappeared in nonirradiated BALB/c recipients shortly after transfer. These BALB/c recipients of CB20 spleen cells (“CB20-primed”) developed lymphocytes which were able to suppress the autochthoneous allotype b production of CB20 irradiated or CB20 nu/ nu or neonatal F 1 (BALB/c ♀ × CB20 Ô) recipients immediately after transfer. Titers decreased with a half life of about 4 days, resembling that of immunoglobulin molecules. The suppression was restricted to the IgG2a isotype of allotype b. Neither the other isotype IgG1 of allotype b, nor, in the reciprocal transfer experiment, IgG1 or IgG2a of allotype a was affected. Anologous transfers between Igh congeneic partners on a C57B1/6 genomic background revealed the same susceptibility of allotype b-producing cells from C57B1/6 donors toward suppression by C57B1/ 6-Igh a mice as recipients. Allotype suppression, induced by cell transfer, is thus unidirectional in that Igh a haplotype mice react against allotype b but not vice versa, and it is isotype-specific, only directed against IgG2a, and not IgG1.

Haemoglobin synthesis in Daphnia magna Straus (Crustacea: Cladocera): ecological differentiation between neighbouring populations

SUMMARY. 1. Variations in the haemoglobin index of two neighbouring populations of Daphnia magna were recorded over a range of dissolved oxygen concentrations (0.5–4.0ml O2 1−1, 20°C). Reciprocal transfer experiments between habitats compared haemoglobin synthesis in situ.2. An inverse relationship was found between the oxygen content of pond water and the haemoglobin indices of laboratory and natural populations.3. Significant genetic differences in the synthesis of haemoglobin were found between the two populations. Animals from the poorly oxygenated habitat (0.8±0.18ml O2 1−1) had consistently higher haemoglobin contents (maximum HI, 87.7±4.5) at all experimental and in situ oxygen levels. D. magna from the well oxygenated pond (4.3±0.59 ml O21−1) had a lowered physiological ability to synthesize haemoglobin (maximum HI, 48.3±4.2). The process of ecological differentiation in Daphnia populations is discussed.

Specificity of the T cells that mediate and suppress adoptive immunotherapy of established tumors.

This study was designed to investigate the specificity of the T cells that express and suppress antitumor immunity in a model of adoptive immunization against established tumors. Results obtained with the P815 mastocytoma, L5178Y lymphoma, and P388 lymphoma showed, in agreement with previous findings from this laboratory, that an intravenous infusion of splenic T cells from immunized mice can cause the regression of a tumor growing in T-cell-deficient mice. So far as specificity of adoptive immunity is concerned, reciprocal passive transfer experiments with these three tumors revealed that T cells from donor mice immunized against the P815 tumor are not capable of causing regression of the P388 tumor or L5178Y tumor, even if both the P815 and L5178Y tumors are growing in the same host. Similarly splenic T cells from mice immunized against the P388 tumor or L5178Y tumor had no effect on growth of the P815 tumor. Suppression of adoptive immunity was also specific, in that passively transferred suppressor T cells from mice bearing a progressive P815 tumor were capable of suppressing adoptive T-cell-mediated regression of the P815 tumor, but not the P388 tumor growing in T-cell-deficient recipients. Reciprocally, P388 suppressor spleen cells from mice bearing a progressive P388 tumor prevented adoptive T-cell-mediated regression of the P388 tumor, but not the P815 tumor. The results indicate, therefore, that the T cells from immunized mice that mediate adoptive antitumor immunity and the T cells from tumor-bearing mice that suppress the expression of this immunity are specific for the tumor that evokes their generation.

Population differences in the timing of diapause: adaptation in a spatially heterogeneous environment.

Populations of the planktonic copepod, Diaptomus sanguineus, live in permanent and temporary freshwater ponds in Rhode Island. All ponds in which they occur become uninhabitable at some time during the year, but the nature and timing of the harsh period varies both spatially and temporally. Females produce discrete clutches either of subitaneous eggs which hatch immediately or of diapausing eggs which hatch the following season. The two egg types show distinct chorion morphologies under transmission electron microscopy. In permanent ponds the copepods start making diapausing eggs in March, one month before rising water temperatures induce planktivorous sunfish to become active. In temporary ponds diapausing eggs are produced, in a complex pattern from May to July, before the water disappears in late summer or early fall.We investigated the spatial scale at which D. sanguineus is adapted to this complex environment. In a reciprocal transfer experiment between temporary and permanent bodies of water, female copepods placed in new ponds made subies of water, female copepods placed in new ponds made subitaneous and diapausing eggs in the same sequence as control females retained in their home ponds. The copepod populations enter diapause at times appropriate for the local habitat conditions they experience, but inappropriate for other, nearby ponds. Transplanted females were unable to sense a change in pond type or to adjust egg production accordingly. We conclude that D. sanguineus populations are adapted to the specific conditions of isolated ponds rather than to a broader geographical region containing several pond types.

Survival and reproduction of the desert pupfish (Cyprinodon n. nevadensis) after acclimation to acid water

AbstractThe tolerance of desert pupfish, Cyprinodon n. nevadensis to acid water was tested by exposing a group of fish for 14 weeks to alkaline water resembling their natural habitat (pH 8.3) and another to sublethal acidity (pH 6.3). The difference in mean times to loss of equilibrium at pH 4.2 (sublethal = 19.2 ± 2.93 hours; control = 17.9 ± 5.37 hours) was not statistically significant, indicating a failure to acclimate to the sublethal acidity.A reciprocal transfer experiment was performed with a sublethal (pH 6.3) and a control group (pH 8.3) to learn whether reproductive performance would compensate for acid stress. Reproductive performance was measured by egg production (eggs gm−1 day−1) and frequency of egg laying. In the first portion of the experiment the two groups were acclimated to their respective conditions for 3 weeks prior to a 3‐week measure of reproductive performance. The two groups were then reversed and tested again for 5 weeks. Reproductive performance of a control group was monitored for the 11‐week experimental period. No adaptation of the reproductive function occurred, since the transferred controls and acclimated sublethals were not statistically distinguishable. The sublethal group did not recover its reproductive capacity after transfer to the control level, suggesting either that permanent damage to some portion of the oogenesis process might have been suffered as a result of the acid exposure, or that the recovery was delayed beyond the 5‐week duration of this portion of the experiment.

Influence of photoperiod on development and larval diapause in the viceroy butterfly, Limenitis archippus

The butterfly Limenitis archippus represents a typical long-day insect. Young larvae show continuous rapid development to the adult when subjected to long-day conditions. However, most of their siblings exhibit slowed larval growth and form hibernacula during the third instar, subsequently entering diapause when reared under conditions of short photoperiod. Preliminary reciprocal transfer experiments indicate that second and early third instar larvae monitor absolute day length to determine whether or not they should enter diapause.

Growth and anthocyanin synthesis in excised Sorghum internodes

Ligh-induced anthocyanin synthesis in excised dark-grown internodes of Sorghum was depressed by the addition of auxin to the incubating medium at physiological concentrations. Both IAA and the synthetic auxin, 2,4-D, reduced anthocyanin yield. Similar results were obtained with isolated internode segments and in internodes incubated with coleoptiles (the major source of endogenous auxins) attached. Auxin increased the duration of the lag phase before anthocyanin synthesis began and reduced the rate during the subsequent linear phase. Elongation continued longer with IAA than without it and anthocyanin formation did not begin until extension growth had ceased or was slowing down in both cases; the rate of anthocyanin synthesis in the IAA solution remained depressed compared with that in buffer even after extension growth had ceased in both.At low concentrations IAA stimulated elongation growth without reducing anthocyanin yield and it is unlikely that the effect of IAA on anthocyanin synthesis results from the increased utilisation in growth of substrates needed for anthocyanin formation. The results of reciprocal transfer experiments from dark to light, and vice versa, showed that the action of IAA was associated with its presence in the incubating medium during the irradiation period. If present only in darkness, before or after transfer to light, IAA did not reduce anthocyanin formation; in the former case total yield was increased by IAA as a result of the stimulation of elongation growth, the concentration of anthocyanin remaining unchanged.GA3 also decreased anthocyanin content; the effect was greater in sections incubated with coleoptiles attached and it is possible that GA3 acts by increasing the concentration of endogenous auxins. However, CCC, which has been reported to decrease endogenous auxin levels, also reduced anthocyanin yield.The effect of IAA was not influenced by the presence of ascorbate in the incubating medium, nor did added ascorbate result in the formation of any acylated cyanidin derivative in internodes maintained in darkness.Possible relationships between light-induced anthocyanin formation and the photo-inhibition of elongation are discussed.