Chicken Blood Cells Research Articles

Study on the dielectric properties of biological cells using the electrokinetic method

AbstractDifferent from hard particles with an ordinary surface structure, a biological cell is a soft particle which can be described as a hard particle covered with an ion‐penetrable surface layer of polyelectrolytes. In this paper, according to the electrokinetic theory of suspension of soft particles, the colloid vibration current (CVI) model of suspended biological cells is investigated. A CVI measurement system is set up in which ultrasonic pulses of different intensities are calibrated and used. The experimental results on electrolyte solutions and cell suspensions show that CVI is closely related to the ion and cell concentration of the sample solution. Along with the increased concentration of ions or cells, the CVI signal increased initially and then decreased for electrolyte solutions, but it was the reverse for a chicken blood cell suspension but stayed almost constant for a spawn suspension. All these phenomena were caused by the interactive electrokinetic polarization of ions and cells under the action of ultrasonic pulses. Through the analysis of the electrokinetic course of the cell suspension, it was found that the amplitude and slope of the electrokinetic curve could be used to characterize the dielectric properties of cells. The electrokinetic model and CVI measurement system are rather feasible, as shown by the experimental results. The electrokinetic measurement method shows a new nondestructive way for studying the charging properties of biological cells, and the method has an inherent advantage for the real‐time study of the biological effects of ultrasound on cells. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A rapid high-precision flow cytometry based technique for total white blood cell counting in chickens

The automated analysis of total white blood cell count and white blood cell differentials is routine in research and clinical diagnosis in mammalian species. In contrast, in avian haematology these parameters are still estimated by conventional microscopic procedures due to technical difficulties associated with the morphological peculiarities of avian erythrocytes and thrombocytes. Both cell types are nucleated and fairly resistant to cell lysis, a prerequisite for automated leukocyte quantification and differentiation by commercial instruments. By using an anti-CD45 monoclonal antibody in combination with selected subset specific markers we have established a simple (no-lyse no-wash single-step one-tube) flow cytometry based technique for high precision chicken blood cell quantification. EDTA-blood samples are diluted, spiked with fluorescence beads and incubated with a mixture of fluorochrome conjugated chicken leukocyte specific antibodies. We demonstrate that total leukocyte numbers as well as thrombocyte, monocyte, T-cell, B-cell and heterophilic granulocyte numbers can be determined by flow cytometry in a single step without prior cell lysis, cell separation or cell washing steps. Importantly, we also show that blood samples can be fixed prior to cell staining which enables shipping of samples making the technology widely available. Comparison of this technique with conventional microscopy revealed superior precision. By comparing leukocyte differentials of two chicken populations and during immune system development after hatch we demonstrate that large sample numbers can be analysed within hours. This technique will help to overcome previous restrictions in immune status analysis in chickens in experimental systems, during vaccine testing and health status monitoring in chicken flocks. Advances in avian genomics should facilitate the development of appropriate tools for other avian species in the future which will make this technique broadly applicable.

Highly efficient dissociation of oxygen from hemoglobin in Tibetan chicken embryos compared with lowland chicken embryos incubated in hypoxia

Oxygen is one of the critical determinants for normal embryonic and fetal development. In avian embryos, lack of oxygen will lead to high fetal mortality, heteroplasia, and cardiovascular dysfunction. Tibetan chicken is a breed native to Tibet that could survive and keep higher hatchability regardless of negative effects of hypoxia. Generally, adaptive animals in high altitudes are characterized by higher hemoglobin concentrations and oxygen affinity. In the present study, the capacity of oxygen supply in late chick embryo (including d 17, 19, and 21) was compared between Tibetan chicken and a lowland breed, Dwarf White chicken, by determining the hemoglobin concentrations and oxygen equilibrium curves in both hypoxic (13% O(2)) and normoxic (21% O(2)) conditions. The results showed that a higher level of hemoglobin concentration was induced by hypoxia in Tibetan chicken embryos, and the hemoglobin could perform with better cooperativity and deliver oxygen to tissues more easily. Further investigation revealed that the carbonic anhydrase II mRNA in red blood cells of Tibetan chicken was increasingly induced to a higher level in hypoxia than that of the lowland breed. These results suggested that the stronger capacity of oxygen dissociation was an important characteristic of Tibetan chicken embryo to survive in hypoxia and the upregulating mode of carbonic anhydrase II mRNA might assist this dissociation. Therefore, for avian at high altitudes, the efficient dissociation of oxygen might reveal another aspect associated with the hypoxia adaptability.

Chicken nucleated blood cells as a cellular model for genotoxicity testing using the comet assay

Mycotoxins can frequently occur in animal feed and human food. T-2 toxin, as the most toxic trichothecene, has been implicated as the causative agent in a variety of animal diseases and is associated with some human diseases. The comet assay was performed as a test for detection of DNA damage caused by T-2 toxin in peripheral blood cells of chicken. The suitability of the comet assay as a biomarker for genotoxic analysis has been applied in studies using human white blood cells. It can be applied to any tissue from which a single cell suspension can be obtained. The method has already been applied to chicken as a foodstuff for detection of irradiation of food containing DNA. However, application of the method on chicken blood cells has not been set up yet. The aim of this research was to develop a protocol for detection of DNA damage induced by T-2 toxin in chicken blood cells. Chickens were administered orally with T-2 toxin and the samples of whole blood were collected at 24 h post treatment. The DNA damage was determined by an increase in the comet parameters in tested animals. Our results show that T-2 toxin had induced significant DNA damage in treated chicken as compared with control animals, indicating that the assay can be used for the assessment of primary DNA damage caused by mycotoxins.

Myb induced myeloid protein 1 (Mim-1) is an acetyltransferase

We have screened protein extracts from chicken blood cells for acetyltransferases. An in gel acetyltransferase assay revealed that a 32 kDa protein, which is more prevalent in whole blood when compared with erythrocyte cells, possessed an auto-acetylation activity. This protein was purified by a series of chromatographic steps, sequenced by Edman degradation and subsequently identified as Myb induced myeloid protein (Mim-1). Mim-1 has similarities to the conserved acetyltransferase motifs found in the GNAT superfamily of proteins and also contains three minimal GK acetylation motifs. These data identify Mim-1 as an acetyltransferase.

Chicken lines differ in production of interferon-like activity by peripheral white blood cells stimulated with phytohemagglutinin

Interferon (INF) activity was evaluated in the supernatants from peripheral white blood cells (WBC) of chickens from six lines. The WBC were cultured in flasks or 24-well plates with medium or medium and phytohemagglutinin (PHA). After 2 to 5 d, duplicate supernatant samples were tested for INF activity, i.e., the log2 titer inhibiting 50% destruction of the cytopathic effect of vesicular stomatitis virus on primary chick embryo fibroblasts. Also triplicate WBC samples were tested for proliferation by [H3]-thymidine labeling and scintillation counting. In the absence of PHA, INF was significant for only two lines, i.e., 7(2) (two trials) and C (one trial). With PHA the level of INF produced was similar if flasks were sampled daily or on successive days. The INF levels were highest using 10 or 20 microg/mL PHA, but line differences were best distinguished using 5 or 10 microg/mL. In three trials there was a low correlation between PHA-stimulated WBC proliferation and INF titer (r > or = 0.30; P < 0.05). It was concluded that supernatants from chicken WBC stimulated with 10 microg/mL PHA contain INF, and inbred Lines 72 and C repeatedly produce more INF than inbred Lines 63 and 15I(5). This is the first evidence for line differences in INF production in chickens, and these lines may be useful for characterization of the relevant genes and their importance in immune response(s) and disease resistance.

Introduction of the Comet assay for the evaluation of oxidative stress, antioxidant effects and environmental pollutants effects on animal cells

DNA damage within single mammalian cells can be one of the earliest signs of a whole range of health problems, including disease, diet and exposure to occupational or environmental toxins. The Comet assay is a relatively simple and inexpensive method for measuring this damage. It works by determining the number of breaks in the strands of DNA within the cell. Cells are embedded in agarose gel on a microscopic slide and washed to remove the cell membranes, soluble cell contents and histones from the nucleus. An electric field is then activated across and the loops of damaged DNA are pulled towards the anode. Epifluorescence microscopy of stained gels shows the image which gives the techique its name: a clump of undamaged DNA (the head) with the loops pulled away, forming a tail of a comet. We report herein the checking of the Comet assay for the evaluation of oxidative stress on chicken, mouse and pig blood cells, pig sperm cells and chicken hepatocytes. We intend to use the Comet assay as a quantitative method in some nutritional experiments with domestic animals including oxidative food components and antioxidants and for the evaluation of some environmental pollutants effects on animal and human cells.

Lead effect on DNA and albumin in chicken blood and the protection of selenium nutrition

Lead effect on DNA and albumin in chicken blood and the protection of selenium nutrition have been investigated to gain insight into initial molecular events following exposure to lead. The concentration of lead used in this paper is 11.6 μg/dL. Single cell electrophoresis technique was utilized to measure DNA strand breaks in chicken blood cells treated with lead, the DNA strand breakage was observed and the percentage of damaged cells increased significantly, organic selenium (Kappa‐selenocarrageenan) had a strong non‐special protection ability to decrease the percentage of damaged cells exposed to lead. Further study with FT‐IR spectroscopy combined with other techniques indicated that with the addition of Pb2+ ion, the chicken serum albumin (CSA) molecule underwent conformational transitions from α‐helix to β‐sheet and turn structures, the binding site of Pb2+ ion in the chicken serum albumin molecule were C=O and C‐N groups of CSA.

Mechanisms underlying the hemolytic and ichthyotoxic activities of maitotoxin.

Maitotoxin (MTX), a putative Ca(2+) channel activator produced by the dinoflagellate Gambierdiscus toxicus showed extremely potent hemolytic and ichthyotoxic activities. Hemolysis of 1% mouse blood cell suspension in saline occurred at 15 nM of MTX. The activity was enhanced six-fold in the presence of 10 microM of Ca(2+) and completely blocked by EDTA2Na, indicating its dependency on external Ca(2+). The MTX-induced hemolysis was little affected by L-type Ca(2+) channel blockers (diltiazem, nifedipine, verapamil) but was strongly inhibited by calmodulin blockers (prenylamine and chlorpromazine) or a phospholipase A2 inhibitor (quinacrine). MTX was mimicked by a calcium ionophore, calcimycin. Based on these results, a series of cellular events triggered by MTX were presumed to occur in the following sequence: increased Ca(2+) entry in cells, activation of calmodulin, promotion of phospholipase A2 activity, and finally destruction of cell membrane resulting from hydrolysis of membrane lipids. The sensitivity of blood cells to MTX varied significantly, dependent on the animal sources. Nucleated blood cells of carps and chickens were 100 times more resistant than those of mammals. LC(50) of MTX to freshwater fish Tanichthys albonubes in Ca(2+) free media (pH 8) was 5 nM but was markedly lowered to 3 pM by raising pH to 8 and increasing Ca(2+) concentration to 2 mM. In a marine environment MTX was 2000 times more toxic to fish than 42-di-hydrobrevetoxin-B (PbTx-3), one of the best known ichthyotoxins of red-tide origins.

Studies on the haemolytic complement of the dromedary camel ( Camelus dromedarius). II. Alternate complement pathway haemolytic activity in serum

Fresh camel serum caused lysis of unsensitised red blood cells (RBC) of chicken, rabbit and guinea pig. Homologous RBC were resistant to lysis. There was only minimal lysis of goat, sheep, rat and cattle RBC. Lysis of heterologous RBC was attributed to the presence of alternate complement activity (ACP) in the serum as adsorption with respective RBC and addition of 10 mM ethylene glycol-bis-tetraacetate (EGTA) in the SVBS diluent did not abrogate the haemolytic activity. Guinea pig RBC were the most sensitive to lysis, giving a mean ACP activity of 41.5±1.8 CH 50 units ml −1. Clotting, followed by storing of blood between 0 and 37°C for 1 h did not significantly affect ACP activity. However, considerable activity was lost when blood was clotted and stored at 44°C for 1 h, or when serum was kept at 4°C for 24 h. Treatment with zymosan, or incubation at 56°C for 30 min inhibited ACP activity. Maximum ACP activity occurred in the presence of 8 mM Mg 2+ in the SVBS-EGTA diluent, at pH 7.3 and incubation time of 2 h at 37°C. Levels of ACP activity were determined in 79 healthy camels of different age groups, ranging from 3 months to 15 years. Calves between 3 months and 1 year of age had higher ACP activity than camels in the age group of 5 years and above. Highest mean ACP activity of 89±7.9 CH 50 units ml −1 were recorded in 1–5 year old camels ( P<0.0001). The lowest ACP activity was observed in the 10–15 year old camels (52±2.9 CH 50 units ml −1). There was no significant difference in the ACP activity between the sexes.

Formation and microscopical application of a fluorescent 1,10-phenanthroline derivative of ruthenium red.

In this work we describe the formation and microscopical application of a fluorescent derivative of Ruthenium Red (RR) obtained by heating the dye in the presence of 1,10-phenanthroline (OP). The RR-OP reaction product showed absorption maxima at 416 and 444 nm and intense fluorescence emission at 578 nm under 440 nm exciting light. Neither RR nor OP solutions alone were fluorescent when excited at 440 nm. Using fluorescence microscopy, chicken blood cell smears stained 5 min with the RR-OP derivative showed the chromatin of erythrocyte nuclei with a bright orange fluorescence under violet-blue (436 nm) exciting light.

Chicken anaemia virus influences the pathogenesis of Marek's disease in experimental infections, depending on the dose of Marek's disease virus.

Eight groups of 1-day-old chickens were inoculated with 0, 250, 5000, or 100,000 white blood cells of chickens infected with Marek's disease virus strain K (MDV-WBC). Four of these groups were additionally infected with 10(5) TCID50 chicken anaemia virus (CAV). At day 14 after inoculation, chickens infected with CAV had reduced haematocrit levels, reduced body weights, and depletion of the thymic cortex and bone marrow. Semi-quantitative immunohistochemical examination of nerves and visceral organs was performed at day 28 by immunoperoxidase staining in which a monoclonal antibody specific for leucocytes was used. CAV significantly enhanced the number of lymphoproliferative lesions induced by 5000 MDV-WBC. In contrast, CAV significantly reduced the number of lymphoproliferative lesions induced by 100,000 MDV-WBC. Comparable results were found at day 61 after macroscopic examination of nerves and visceral organs. These findings show that the pathogenesis of MD in experimental infections appears to be enhanced or inhibited by CAV, depending on the dose of MDV.

The fine structure of broiler chicken blood cells, with particular reference to basophils, after severe heat stress

The fine structure of blood cells, with particular reference to basophils, was studied in broiler chickens before and after they had been subjected to heat stress. Granule counts in basophils after heat treatment showed a significant reduction in their total numbers compared with pre-heat treatment. This depletion of granules corresponded with evidence of degranulation seen at the ultrastructural level. Of the three types of basophilic granules described, only the type I electron-dense, homogeneous variety of granule was significantly reduced in number. After heat stress, there was a significant increase in heterophil lobulation. In several birds there was also evidence of cytoplasmic fragmentation in the form of portions of cells containing granules but no nuclei, lying free in the circulation. Damaged mitochondria, not seen before heat treatment, were frequently observed in the cells. Monocytes also showed significant increases in cytoplasmic lipid droplets after heat stress compared with pre-heat treatment, suggesting the onset of possibly early fatty degeneration. However, there was no evidence of increased pseudopodia or pinocytotic activity in these cells. With heat stress, there was a significant reduction in the numbers of electron-dense granules in the small lymphocytes. Despite there being a smaller proportion of circulating eosinophils after heat stress, which was considered to be the result of an immediate stress response, no significant differences were evident between pre- and post-heat treatment in the cells. The red cells and thrombocytes from post-heat-stressed broilers were significantly longer and thinner compared with pre-heat treatment due possibly to dehydration. The dimensional and ultrastructural changes identified in the cells after heat stress question their effective functional ability in raising an immune response under such circumstances.

Contact-haemolysin production by entero-invasive Escherichia coli and shigellae

Entero-invasive Escherichia coli (EIEC) and shigellae were tested for contact-haemolysin (CH) with red blood cells (RBCs) of guinea-pig, rabbit, rat, mouse, monkey, man, sheep and chicken; all bacteria showed the best lysis with guinea-pig RBCs. The best culture medium for CH activity of shigellae was tryptic soy broth, and for EIEC it was casamino acid-yeast extract broth with 1 mM CaCl2. CH production by all species was best at the slightly alkaline pH which is optimal for growth; it was also dependent on the presence of a large (140-Mda) plasmid. Pre-treatment of bacteria with homologous antisera inhibited CH activity. Various treatments of bacterial cells and RBCs suggested that CH may be a protein molecule, and that a chitotriose-like moiety may serve as CH receptor. RBCs that were incubated with bacteria at 4 degrees C, or with heat-killed bacteria at 37 degrees C, were not lysed; also, isolated cell-surface components (lipopolysaccharide and outer-membrane protein) did not lyse RBCs. This suggests that metabolically active cells are required for CH activity. Production of CH by both EIEC and shigellae is consistent with a common mechanism for the virulence of these organisms.

Characterization of a New Fimbrial Antigen Present in Escherichia coli strains Isolated from Calves*

Thirteen Escherichia coli strains isolated from calves with diarrhoea, supposed to carry a common antigen were examined for their hemagglutinating activity and compared by bacterial agglutination, double diffusion in two dimensions and by crossed immunoelectrophoresis (CIE). Two of the strains were examined also in the electron microscope. Most of the strains agglutinated red blood cells of horse, ox, guinea pig and chicken, of which the agglutination of ox erythrocytes was mannose-resistant (MRHA). None of the strains agglutinated human erythrocytes. All strains with MRHA of ox red blood cells, regardless to their O:K:H antigens could be agglutinated in unabsorbed or absorbed antisera produced against cultures C1209 (020:K-:H9) and C1213 (09:K36:H-) when live cells as antigens were used. None of these sera agglutinated reference strains carrying K88, K99, 987P, F41 or FY (Att25) antigen respectively. By the double gel diffusion test and by CIE in extracts (60 degrees C) of the strains a common heat labile antigen, responsible for the MRHA of ox red blood cells was identified. Electron microscopy revealed that this common antigen was represented by thin, long, hair-like fimbriae on cells of E. coli C1213, and that specific homologous antibodies attached to these fimbriae.

Cytochemical properties of chicken blood cells resembling both thrombocytes and lymphocytes.

Generally accepted criteria were used to identify typical nucleated thrombocytes and typical small lymphocytes in chicken-blood smears subjected to modified-Wright staining. Other cells, here referred to as "intermediate cells," were difficult to classify because in some aspects they resembled thrombocytes while they also had features typical of small lymphocytes. The "intermediate cells" had small, round or oval nuclei with coarsely condensed chromatin, characteristic of both thrombocytes and small lymphocytes. In addition, "intermediate cells" had moderately abundant cytoplasmic volumes, typical of thrombocytes but blue cytoplasm lacking both granules and vacuoles, which is characteristic of small lymphocytes. It made little difference to the thrombocyte count whether these cells were classified as thrombocytes or small lymphocytes; however, this decision made a substantial difference to the lymphocyte count in some chicken-blood smears. Most "intermediate cells" (351 of 410 cells examined) were nonfluorescent after treatment with formaldehyde gas. Furthermore, most "intermediate cells" failed to acquire characteristic pigments when subjected to either Grimelius staining (179 of 204 cells examined) or periodic acid-Schiff staining (173 of 206 cells examined). Typical small lymphocytes reacted in the same way, failing to fluoresce after gaseous formaldehyde treatment (65 of 65 cells examined) and failing to react during Grimelius staining (41 of 44 cells examined) or periodic acid-Schiff staining (21 of 21 cells examined). In contrast, almost all typical thrombocytes became fluorescent in response to gaseous formaldehyde (709 of 718 cells examined) and gave positive reactions when subjected to Grimelius staining (381 of 382 cells examined) or periodic acid-Schiff staining (322 of 326 cells examined). These findings suggested that "intermediate cells" should be classified as lymphocytes in differential cell counts.

Immunofluorescence examination of beta tubulin expression and marginal band formation in developing chicken erythroblasts.

Chicken erythrocyte beta tubulin, a tubulin variant with unique biochemical and assembly properties, is found to be specifically contained in two chicken blood cell types--erythrocytes and thrombocytes. The beta tubulin variant is absent or present in low amounts in a variety of white blood cell types and other body tissues, as determined by immunofluorescence microscopy and a semi-quantitative immunoblotting procedure. During differentiation in the marrow the beta tubulin variant appears suddenly in mid-stage erythroblasts at the onset of hemoglobin synthesis, and forming marginal bands are seen in all subsequent polychromatophilic erythroblast stages. The developmental sequence of events in marginal band formation entails microtubule nucleation at the centrosome, followed by microtubule elongation, consolidation of loose parallel microtubules into a compact bundle, and microtubule association with the cell membrane.

A simple method for the fluorescence analysis of nucleic acid-dye complexes in cytological preparations.

This communication describes a simple method for recording fluorescence emission spectra of cytological preparations using a conventional fluorescence spectrophotometer. The emission characteristics of "in situ" complexes between some basic fluorochromes (DAPI, 33258 Hoechst, acridine orange, pyronin Y, and ethidium bromide) and nucleic acid containing structures from smears of chicken blood and Ehrlich tumor cells (chromatin, basophilic cytoplasm) are briefly described.

Perisinusoidal cells in a three-dimensional organization of the adrenal cortex in the monkey.

The adrenal cortex in the macaque monkey was examined under the SEM and TEM to elucidate the surface fine structure of perisinusoidal cells in a three-dimensional organization of the cortex. Parenchymal cells in polyhedral form were arranged in acini in the zona glomerulosa, or in the laminae of closely stacked cells in the zona fasciculata and reticularis. Those acini and laminae were accompanied by sinusoids lined only with an endothelium. Endothelial cells were composed of a protruded perikaryon and a thin layer of peripheral cytoplasm in sieve plates with numerous fenestrations. The perikaryon was sometimes equipped with groups of fenestrated disc-like protrusions. Fine collagen fibrils were distributed in the perisinusoidal space, which was a continuous, slit-like lacune between the endothelial and parenchymal cells. In the perisinusoidal space or intercellular spaces among parenchymal cells were seen two types of perisinusoidal cells: the stellate interstitial cells with several spiny, or attenuated processes entangled with collagen fibrils, and the monstrous wandering cells usually associated with pseudopodia-like processes. The cytoplasm of the interstitial cells showed a structure similar to that of fibroblasts, and contained small numbers of lipid droplets. Intravenously injected chicken blood cells were phagocytized by macrophages on the sinusoidal lining. The fine cytological structure of the macrophages was almost the same as that of the wandering cells. The present findings suggest that the interstitial cells are fibroblastic in nature and belong to the vitamin-A storing cell system, and that the wandering cells are macrophages derived from hematogenous monocytes.

Ontogeny of con A and PHA responses of chicken blood cells in MHC-compatible lines 6(3) and 7(2).

The development of T cell responsiveness to Con A and PHA was examined in two MHC-compatible inbred chicken lines, RPRL 6(3) and 7(2), at ages 2 to 118 days posthatching. These lines are respectively resistant or susceptible to Marek's disease, a naturally occurring, virally induced T cell lymphoma. Between-line comparisons were made of optimal in vitro responses of diluted serum-free blood cells to each mitogen in two groups of chicks tested over ages 2 to 63 and 41 to 118 days. Over 2 to 63 days, Con A responses increased with age at the same rate in each line, but 7(2) responses averaged 2.3 times higher than 6(3). The increase with age was dependent on blood lymphocyte counts, which also increased with age in parallel in both lines. In contrast, the between-line difference in responsiveness was dependent on intrinsic reactivity of cells as well as lymphocyte counts. Covariance analysis was used to estimate that line 7(2) was 1.4 times higher than 6(3) in intrinsic cell reactivity, after accounting for the effect of the twofold higher blood lymphocyte counts in 7(2), and that this intrinsic difference contributed almost one-half the total difference. Over 41 to 118 days Con A responses no longer increased with age, although lymphocyte counts were still increasing, and the line difference (2.6 times) was now almost entirely contributed by a 2.3-fold superiority of 7(2) blood cells in intrinsic reactivity. The line difference in PHA responses was the reverse of the above in young chicks, with 6(3) responses greater than 7(2) in spite of lower lymphocyte counts. In additional chicks tested over 5 to 26 days, intrinsic reactivity of 6(3) cells to PHA averaged 4.5 times higher than 7(2). There was an abrupt decline in intrinsic reactivity of line 6(3) blood cells between 26 and 41 days to a level equal with 7(2). After this age, line 7(2) responses were 1.8 times greater than those of 6(3), and this difference was dependent solely on lymphocyte count differences. The results suggest that different gene systems mediate blood cell responses to PHA as compared with Con A. The pattern of developmental differences between inbred lines indicates the existence of distinct or partly overlapping T cell subsets with different reactivities to PHA or Con A, and of higher suppressor activity of adherent cells in line 6(3) blood. Both these differences may be related to line 6(3) inherited resistance to Marek's disease.