SC Chickens Research Articles

ОЦЕНКА ГЕНЕТИЧЕСКИХ ПАРАМЕТРОВ КУР ПРИ ИСПОЛЬЗОВАНИИ МИКРОСАТЕЛЛИТНЫХ МАРКЕРОВ

The purpose of the study is improvement of pedigree accessory of identification process of poultry with use of microsatellite markers. The analysis was performed with 9 breeds of chickens (n=268) for 16 markers. The studies were performed with the chicken breeds, such as: the Black and White Аustralorp (BWAus), Black Australorp (BAus), Kulangi (Kul), Czech Gold (CzG), Blue Andalusian (BAnd), Naked Neck (NN), Silver Campine (Breukel) (SC), Black Bearded Russian (BBRus), and Minorca (Min). There were 29 to 30 poultry in each experimental group. The researches were carried out at the Molecular Genetics Laboratory, Ernst All-Russia Research Institute of Animal Husbandry. Separation and detection of amplification products were performed on an Applied Biosystems АВI3130xl Genetic Analyzer (USA). Statistical data processing was performed using GenAlEx software version 6.4. The work examined genetic diversity of chickens (average number of alleles, number of effective alleles, the level of homo - and heterozygosity, etc.), using microsatellite loci. It should be noted that the average number of alleles in the study ranged from 6.06±0.050 in the BAnd bantams to 7.81±0.73 in the NN chickens, while the number of informative alleles ranged from 3.63±0.30 in the BAnd bantams to 5.44±0.34 in the SC chickens. High informativeness of 16 selected loci performance was noted during the research; the number of alleles ranged from 8 (locus MCW0037) to 25 alleles (locus MCW0183), depending on the locus. The conducted research allowed us to identify the presence of private alleles in the studied breeds of chickens, which were discovered in poultry within 7 of 9 breeds with frequencies of 1.7 to 67.7%. The expected and observed levels of heterozygosity were calculated to assess the variation of the investigated species more accurately; their mean values reached 66.9 and 37.1%, respectively. Breeds of chickens affiliated to their populations were identified based on analysis of 16 microsatellite markers; the estimates varied from 79.3% to 100.0%. Therefore, the use of microsatellite loci in chicken breeding can give more opportunities to create pedigree poultry flocks within the genetic pool of breeds.

Nitric oxide production by macrophages stimulated with Coccidia sporozoites, lipopolysaccharide, or interferon-gamma, and its dynamic changes in SC and TK strains of chickens infected with Eimeria tenella.

Nitric oxide (NO) is an important mediator of innate and acquired immunities. In the studies reported here, we quantified NO produced in vitro by chicken leukocytes and macrophages and in vivo during the course of experimental infection with Eimeria, the causative agent of avian coccidiosis, and identified macrophages as the primary source of inducible NO. Eimeria tenella-infected chickens produced higher levels of NO compared with noninfected controls. In Eimeria-infected animals, SC chickens produced greater amounts of NO compared with infected TK chickens, particularly in the intestinal cecum, the region of the intestine infected by E. tenella. Macrophages that were isolated from normal spleen were a major source of NO induced by interferon (IFN)-gamma, lipopolysaccharide (LPS), and E. tenella sporozoites. Macrophage cell line MQ-NCSU produced high levels of NO in response to Escherichia coli or Salmonella typhi LPS, whereas the HD-11 macrophage cell line was more responsive to IFN-gamma. These findings are discussed in the context of the genetic differences in SC and TK chickens that may contribute to their divergent disease phenotypes.

Interleukin-2 production in SC and TK chickens infected with Eimeria tenella.

SC and TK inbred chicken strains display differential protective immunity to coccidiosis, SC being more resistant and TK susceptible to disease. In this study, the association between interleukin (IL)-2 and disease phenotype was assessed by cytokine quantification in serum, duodenum, cecum, and spleen cell cultures of SC and TK chickens experimentally infected with Eimeria tenella. In general, after primary infection, SC and TK strains produced equivalent amounts of IL-2 in all sources examined. However, after secondary infection, SC animals displayed significantly greater IL-2 levels in serum and the duodenum compared with strain TK. IL-2 production after reinfection with Eimeria may be an important factor contributing to the genetic differences in coccidiosis between SC and TK chickens and provides a rational foundation for cytokine-based immunotherapeutic approaches to disease control strategies.

Eimeria tenella infection induces local gamma interferon production and intestinal lymphocyte subpopulation changes.

The role of intestinal lymphocytes and gamma interferon (IFN-gamma) production in protective immunity to Eimeria tenella infection was evaluated in two inbred strains of chickens (SC and TK) that display different patterns of susceptibility to coccidiosis. Oral inoculation of either strain with E. tenella led to parasite invasion of the intestinal cecum and cecal tonsils. Greater fecal oocyst shedding was seen in TK chickens. Flow cytometric analyses of cecal tonsil lymphocytes demonstrated greater numbers of CD4(+) and T-cell receptor gammadelta-positive (TCR1(+)) cells in SC chickens and elevated numbers of CD8(+) and TCR2(+) cells in TK chickens following primary infection. IFN-gamma mRNA expression was significantly increased in cecal tonsil and intraepithelial lymphocytes at days 6 and 8, respectively, after primary infection in SC compared to TK chickens. While no differences were noted between cecal tonsil lymphocytes of the two strains following secondary infection, TK chickens showed elevated IFN-gamma transcript levels in intestinal intraepithelial lymphocytes at this time. Selective depletion of CD4(+), but not CD8(+), cecal tonsil lymphocytes in SC chickens resulted in a reduced IFN-gamma mRNA expression, indicating that CD4(+) cells are the primary source of this cytokine. Collectively, these results indicate that local lymphocyte responses and production of IFN-gamma are influenced by host genetic factors.

Changes in local IFN-γ and TGF-β4 mRNA expression and intraepithelial lymphocytes following Eimeria acervulina infection

Inbred chickens SC (B 2B 2) and TK (B 15B 21) display different levels of susceptibility to Eimeria acervulina infection. Following primary and secondary infections, SC chickens showed significantly lower oocyst production compared to TK chickens. Both strains produce significantly fewer oocysts during secondary infection (si) indicating that a protective host immune response had developed subsequent to primary infection (pi). To elucidate the immunologic differences between SC and TK chickens that may account for their different levels of disease susceptibility, cellular and molecular parameters of intestinal immunity were compared. CD4 T-lymphocytes increased significantly and more rapidly post-pi and si in SC relative to TK chickens during the later stages of infections. However, later during the infections, CD4 cells were higher in TK compared to SC chickens. Although the percentage of CD8 lymphocytes increased in both strains after pi, following si the percentage of these cells continued to increase in SC chickens but showed a marked decrease in TK chickens. Contrary to the effects on CD4 cells, the percentage of TCR1 cells was higher in TK chickens early after pi while the same cell subset was higher in SC chickens later following infection. The percentages of TCR2 cells were significantly higher in both strains following pi. At the molecular level, IFN-γ mRNA expression in caecal tonsils and splenic lymphocytes was generally higher in SC compared to TK chickens following E. acervulina infection, while intraepithelial lymphocytes from the duodenum demonstrated reduced levels of this cytokine in both the strains, particularly following pi. TGF-β4 mRNA levels generally increased in lymphocytes from the caecal tonsils, spleen and duodenum from both the strains. These differences in lymphocyte subpopulations and cytokine mRNA expression between SC and TK chickens following E. acervulina infection indicate a complex genetic control of the native immune response to coccidiosis.

Genetic Influence on Nitric Oxide Production during Eimeria tenella Infections in Chickens

Studies were carried out to assess the importance of nitric oxide (NO) production in vivo in resistance to Eimeria tenella infections through treatment of resistant SC and susceptible TK strains of chickens with compounds proven to be effective inhibitors of induced nitric oxide synthase. The SC strain produced higher levels of plasma NO2- + NO3- in response to primary infection than did the TK strain. SC chickens were also more responsive in reduction of NO2- + NO3- levels and increased oocyst output in response to treatments with S-methylisothiourea or NG-methyl-L-arginine (LNMA) during primary infection. However, the SC strain, regardless of drug treatment, consistently yielded higher oocyst output during primary infection, indicating it could be susceptible to a higher parasite burden. On the other hand, the SC strain seemed to develop immunity more rapidly than the TK strain, in that oocyst output was decreased in both untreated and LNMA-treated chicks upon challenge infection compared with that of the TK strain. Oocyst output from both SC and TK strains was further decreased by LNMA treatment during challenge infection rather than increased, suggesting minimal involvement of NO production in the immune response to challenge. These results indicate that NO production during primary E. tenella infection may be only one of several immune responses and may not be the main anticoccidial effector.

In vivo Role of Tumor Necrosis-Like Factor in Eimeria tenella Infection

The effect of tumor necrosis-like factor (TNLF) on the pathogenesis of coccidiosis was investigated. Injection of crude chicken TNLF enhanced the weight loss caused by Eimeria tenella infection. Rabbit polyclonal antibody against recombinant human tumor necrosis factor-alpha (rhTNF) partially restored E. tenella-induced weight loss in SC chickens, but not in TK chickens. However, injection of chickens with chicken TNLF, rhTNF, and rabbit serum against rhTNF had no significant effect on cecal lesions. Both SC and TK chickens produced circulating TNLF following primary, but not secondary infection, and SC chickens showed higher level of TNLF production than TK chickens. Peripheral blood leukocyte-derived macrophages from SC and TK chickens produced a significant amount of TNLF compared to the preinfection condition when cocultured with sporozoites. In general, macrophages from SC chickens produced higher levels of TNLF than those from TK chickens. No significant difference was observed between primary and secondary infection. These results suggest that the excessive TNF production may be involved in weight loss caused by E. tenella infection in SC chickens.

Chicken interferon-mediated induction of major histocompatibility complex Class II antigens on peripheral blood monocytes

Conditioned medium containing immune interferon (IFN) activity was prepared by stimulating spleen lymphocytes obtained from inbred SC chickens with 10 μg concanavalin A (Con A) for 48 h. Pretreatment of spleen cells with monoclonal antibody against CD4, but not CD8, abrogated IFN production suggesting that CD4+ lymphocytes are responsible for immune IFN production. Immune IFN was purified 25-fold from Con A conditioned medium using controlled-pore glass column chromatography resulting in an increase in specific antiviral activity from 7 to 3290 units mg −1. Partially purified immune IFN retained antiviral and macrophage-activating factor (MAF)-like activities. Normal peripheral blood macrophages, when cultured in the presence of partially purified immune IFN, showed a dose-dependent increase in cell surface major histocompatibility complex Class II antigen expression by flow cytometry. Northern blot analysis of mRNA obtained from IFN-treated macrophages showed a concomitant increase in Class II gene expression. This effect was more obvious in cells induced for 48 h than in those induced for 24 h. These results strongly suggest the existence of an avian homologue of the MAF-like activity.

Analysis of Eimeria acervulina-induced changes in the intestinal T lymphocyte subpopulations in two chicken strains showing different levels of susceptibility to coccidiosis

The major T lymphocyte subpopulations expressing CD8, CD4, or antigen-specific T cell receptor ( TCR) heterodimer αβ (TCR2) or γδ ( TCR1) were assessed in duodenum intraepithelium of two inbred chicken strains, SC and TK, by single- and double-label immunofluorescence ( IF) at various times after oral inoculation with Eimeria acervulina. The duodenum intraepithelial T lymphocytes ( IEL) expressing the CD8 antigen (cytotoxic/suppressor T cells) increased in the SC and TK chickens following primary infection. However, a significant increase in the duodenum CD8 + IEL occurred in the SC chickens which manifested as a lower level of oocyst production compared to the TK chickens following primary and challenge infections. The CD4 + (T helper) cells increased seven days after primary infection in SC and TK chickens, and in TK chickens seven days after challenge infection. Two colour immunofluorescence analysis of duodenum IEL at 10 days after challenge infection revealed that the majority of CD8 + IEL expressed the TCR2 antigen. Furthermore, the SC chickens showed increased TCR2 +CD8 + cells shortly following challenge with E acervulina. These results suggest that variations in T cell subpopulations may reflect eimerian infection-related changes in the gut-associated lymphoid tissues and that a significant increase in CD8 + IEL in SC chickens may reflect enhanced acquired immune status in SC chickens compared to TK chickens.

Protection against Apoptosis in Chicken Bursa Cells by Phorbol Ester in Vitro

Like the thymus, the bursa of Fabricius is a site of massive lymphopoiesis accompanied by cell death in vivo. In the present study we have, therefore, examined whether chicken bursa and thymus cells exhibit apoptosis. Bursa and thymus cells from SC chickens, 4-10 weeks of age, were incubated for 8-24 hr with various reagents. Genomic DNA was isolated, electrophoresed in 3% Nusieve agarose gels, and examined for patterns of DNA fragmentation. A laddering of DNA in multiples of 200 base pairs, indicative of apoptosis, was observed particularly with bursa and, to a much smallest extent, with thymus or spleen cells. These patterns of DNA fragmentation from bursa cells could be prevented by adding phorbol myristate acetate (PMA) but not by its inactive analog 4α-PMA during culture. Ionomycin is not required for this effect and, alone, appears to be slightly toxic for bursa cells, although it does not inhibit the effect of PMA. PMA did not affect the degree of DNA fragmentation in spleen or thymus cells. The addition of the protein kinase C (PKC) inhibitor staurosporine abolished both the preventive effect of PMA on apoptosis and its protective effect on bursa cells, as assayed by [ 3H]thymidine incorporation 24-48 hr after the initiation of cultures. PKC inhibitors also prevented the proliferation-inducing effect of PMA + ionomycin on spleen cells. It is concluded that the activation of protein kinase C and perhaps other kinases protects against apoptosis in cultured bursa cells.

Postnatal development of T-lymphocyte subpopulations in the intestinal intraepithelium and lamina propria in chickens

Postnatal development of various T-lymphocyte subpopulations expressing CD3, CD8, CD4, and antigen-specific TCR heterodimers αβ (TCR2) or γδ (TCR1) was investigated in two different inbred chicken strains, SC and TK. The ratios of jejunum T-cells expressing TCR1 to TCR2 in the intraepithelium of SC and TK strains gradually increased after hatching and were 3.40 and 4.28 by 12 weeks in TK and SC chickens respectively. The ratios of TCR1 + to TCR2 +-cells in intraepithelium and the lamina propria in SC chickens were 0.96 and 1.23 at 8 weeks and 4.29 and 2.15 at 12 weeks, respectively. Jejunum intraepithelial lymphocytes expressing the CD8 antigen increased gradually until 4–6 weeks of age and subsequently declined as chickens aged. CD4 +-cells represented a minor subpopulation among the intestinal lymphocyte subpopulations. Therefore, the composition of various T-cell subpopulations in the intestine depended upon host age, the regions of the gut examined and host genetic background. These results suggest that changes in T-cell subpopulations in the intestine may reflect age-related maturation of the gut-associated lymphoid tissues.

Proliferative response of T cells from tumor-immune chickens to carcinogen-induced fibrosarcoma cells

Immunity to carcinogen-induced transplantable fibrosarcomas (CHCT-NYU-4, -97, -36 and -20) in SC chickens was studied by the ability of spleen cells from NYU-4 or -97 immune chickens to proliferate in response to tumor cells in vitro. Spleen, but not peripheral blood cells, from NYU-4 immune chickens proliferated significantly more vigorously to gamma-irradiated NYU-4 cells than did cells from normal chickens. The proliferative response was not much affected by addition of indomethacin. Spleen cells from NYU-4-immune agammaglobulinemic (A gamma) chickens exhibit the same ability to proliferate in presence of gamma-irradiated NYU-4 tumor cells. Analysis of the phenotype of the T-cell component involved in proliferation showed that the proliferative response was significantly decreased by removal of CT4+ cells through indirect panning. Removal of CT8+ cells enhanced background proliferation without affecting the total thymidine incorporation in the presence of tumor cells. Immune spleen cells usually gave highest responses to the immunizing tumor, but also exhibited cross-reactivity to cells from other individual tumors induced by the same carcinogen.

Wing web or intravenous inoculation of chickens with v- src DNA induces visceral sarcomas

We have previously found that sarcomas localized to visceral organs frequently arise following wing web inoculation of Rous sarcoma virus. This observation prompted an investigation of whether visceral sarcomas are also inducible by wing web inoculation of a subgenomic viral DNA fragment (v- src DNA) that includes v- src but lacks genes encoding viral structural protein. For this analysis, line SC chickens were inoculated with v- src DNA at 1–2 days posthatch and monitored for 9 weeks. Ninety percent of the chickens developed wing web (primary) tumors at the site of inoculation and, of these, about 30% exhibited visceral tumors. All tumors were histologically identifiable as sarcomas, and both the primary and visceral sarcoma cells were specifically reactive with two monoclonal antibodies elicited to different peptide fragments of pp60 v- src . In a separate set of experiments, visceral sarcomas were also observed in about half of the line SC chickens that had been inoculated intravenously with v- src DNA. These results indicate that exogenous progeny virus production is not required for v- src-induced, visceral sarcoma formation. In addition, they demonstrate that intravenous inoculation of v- src DNA is a means to achieve rapid and widespread, disseminated sarcoma growth.

Eimeria acervulina: Evaluation of the cellular and antibody responses to the recombinant coccidial antigens in B-congenic chickens

The roles of major histocompatibility complex (MHC) and non-MHC-linked genes in the genetic control of disease susceptibility and the development of protective immunity to Eimeria acervulina infection were investigated in six 15I 5- B congenic and four different strains of chickens characterized for the MHC. When oocyst production was assessed, wide variations were noted following initial and challenge infections among the strains of chickens tested. In general, 15.N-21, 15.P-13, B21, B19, SC, and FP chickens were protected following challenge infection whereas 15I 5, 15.P-19, 15.7-2, and 15.6-2 chickens were not. Strains of chickens sharing a same B haplotype on different genetic backgrounds did not show comparable levels of protection. These results lead to the view that non-MHC-linked genes have a profound influence on the outcome of the host response to E. acervulina infection. Chickens infected twice at 1-month intervals by an oral inoculation with E. acervulina developed both coccidial-specific antibody and T-cell responses. E. acervulina infected chickens showed T-cell-mediated immune responses to the intact sporozoites as well as to recombinant proteins, p130 of sporozoites and p150 of merozoites. Both p130 and p150 antigens have been identified and characterized previously. Sera obtained from all infected chickens recognized the p150 merozoite protein, but not the p130 sporozoite protein in immunoblots. In general, the cellular response, but not the antibody response to the p150 recombinant surface merozoite antigen correlated with the degree of protection following the challenge infection. These results suggest that the strains of chickens having improved protection against challenge infection demonstrate higher T-cell responses to the recombinant surface merozoite protein, p150.

Transfer of experimental glomerulonephritis in chickens by mononuclear cells

We have produced experimental autoimmune glomerulonephritis (EAG) in histocompatible SC chickens by immunization with different types of glomerular antigen. The development of EAG was time, but not antigen, dependent. Transfer of mononuclear cells from spleens and kidneys of nephritic animals resulted in EAG in naive recipients. Transferred EAG developed earlier than in immunized donors and was not associated with circulating or bound anti-GBM antibodies. Control recipients did not develop disease from control cells alone, soluble antigen, or antigen plus control cells. The cells which transferred EAG appeared morphologically by light and electron microscopy to be lymphocytes, sedimented as lymphocytes, were positive with anti-serum to thymocytes but negative with anti-bursa anti-serum, stained as T-cells with monoclonal antibodies and underwent blast transformation in response to mitogen and GBM antigen. Other organ specific diseases have been transferred by cells alone; to our knowledge this is the first description of glomerulonephritis transferred by cells alone. This new pathogenetic process may play an important role in the development of glomerulonephritis in other animal models as well as in humans.

Influence of Inoculation Dose, Inoculation Schedule, Chicken Age, and Host Genetics on Disease Susceptibility and Development of Resistance to Eimeria tenella Infection

Various parasite- and host-related factors influencing disease susceptibility and development of protective immunity against Eimeria tenella infection were investigated in two inbred strains of chickens. Chickens that received a primary inoculation of 10(3), 10(4), or 10(5) oocysts showed a significant reduction in packed cell volume and produced significantly more oocysts than chickens inoculated with fewer oocysts. Younger chickens were as susceptible as older chickens to identical parasite doses. However, upon a secondary inoculation 5 weeks following primary inoculation, FP chickens 1 to 21 days old at the time of primary inoculation developed resistance to reinfection, whereas SC chickens less than 3 weeks old at the time of primary inoculation were highly susceptible to secondary infection. Flow cytometric analysis of spleen lymphocytes showed a substantial reduction in T-cell number in 1-day-old SC but not FP chickens. Furthermore, 1-week-old SC chickens showed depressed mitogenic responses to concanavalin A compared with 1-week-old FP chickens. There was no significant difference between SC and FP chickens in speen B-cell number, regardless of age.

Comparative natural killer cell activities of thymic, bursal, splenic and intestinal intraepithelial lymphogytes of chickens

The natural killer (NK) cell activities of spleen, thymus, bursa, peripheral blood and gut intraepithelial lymphocytes (IEL) from FP and SC chickens were investigated in 4-hr and 16-hr 51Cr release assays. Target cells were 4 different tumor cell lines derived from either an avian leukosis tumor transplant (LSCC-RP9, LSCC-RP12) or from Marek's disease lymphomas (MDCC-MSB-1, MDCC-CU36), Great variability in cytotoxic potential was observed among NK cells of different lymphoid organs. NK cell cytotoxicity varied depending upon the type of effector cells, type of target cells, the ratio of effector to target cells, and the age and genetic background of chickens. Substantial levels of NK cell activity were detected in splenn and gut IEL of SC chickens in a 4-hr assay. In contrast, the NK cytotoxicity in gut IEL of FP chickens was not detectable until 16 hr after incubation. The ranges of target cell specificity demonstrated by IEL, spleen, thymus and bursa NK cells were similar to one another and, in general, the level of cytotoxicity increased with incubation time. Thymus and bursa NK cell activity of both SC and FP chickens was not detectable in a 4-hr assay but substantial NK cell activity was demonstrated in a 16-hr assay. The results of the present study demonstrate that various lymphoid organs of chickens, such as spleen, thymus, bursa, and gut intraepithelium, contain subpopulations of cells that can mediate spontaneous cytotoxicity.

Functional and structural alterations of the nervous system induced by avian retrovirus RAV-7

Chickens infected as embryos with RAV-7 developed neurological signs including ataxia, lethargy, and imbalance. Evoked spinal cord potentials for RAV-7 infected SC chickens were considerably slower (64.8 m/s) than for uninfected SC (103.4 m/s), genetically hypothyroid (OS) (93.9 m/s) or special C (95.1 m/s) chickens. Conduction velocity measurements of sciatic nerves showed normal values for all the chickens examined in this study. Histopathological studies revealed non-suppurative meningoencephalomyelitis in RAV-7 infected SC chickens. The inflammatory infiltrate consisted of lymphocytes, macrophages, and occasional plasma cells. The cells in the infiltrate reacted with mouse monoclonal antibodies directed against la and T-cell antigens. Astrocytic hypertrophy and hyperplasia, demonstrated by the use of monoclonal antibody specific for glial fibrillary acidic protein (GFAP), was associated with the CNS lesions. The results of this investigation indicate that RAV-7 causes significant central nervous system lesions and functional impairment in the infected chicken. This system may serve as a useful model for studying retrovirus-induced neurological dysfunction.

Experimental Autoimmune Glomerulonephritis in Chickens. II. Adoptive Transfer of Disease with Mononuclear Cells

Autoimmune glomerulonephritis was induced in donor chickens by immunization with chicken, human, turkey or bovine glomeruli. Lymphocytes from the kidneys of each group and the spleen of donors immunized with chicken glomeruli were isolated and injected intravenously into six-week old syngeneic SC chickens. The disease was transferred to bursectomized/non-bursectomized recipients by cells from donors immunized with chicken and bovine glomeruli but not by cells from chickens immunized with human and turkey glomeruli. The transferred disease correlated with interstitial infiltrates in donors. No antibody was detected on the glomerular basement membrane or in the circulation of any recipients. Glomerulonephritis in this model can be transferred by specifically sensitized T lymphocytes alone without antibody. This new pathogenic process may play an important role in the development of glomerulonephritis in other animal models as well as in man, where minimal or no immune deposits are observed despite glomerulonephritis.

Suppressor T cells with histamine type II receptors in chickens bearing chemically induced fibrosarcomas.

Immunity to a local (wing web) challenge with transplantable, chemically induced tumors, such as CHCT-NYU-4, can be transferred to histocompatible SC chickens with intravenously injected splenic T cells from tumor-immune chickens. Simultaneous iv injection of splenic T cells from chickens bearing progressively growing CHCT-NYU-4 prevents the expression of this adoptive systemic tumor immunity. The splenic suppressor T cells are B-L(Ia) positive and adhere to dishes coated with cimetidine-protein conjugate, suggesting that they bear type II histamine receptors (H2R). Intravenous injection of gamma-irradiated CHCT-NYU-4 cells 7 days prior to a local challenge with the same tumor promotes growth of a normally suboptimal tumor cell dose such that the incidence of progressive tumor growth is significantly increased. Concomitant treatment with the H2R antagonist, ranitidine, inhibits tumor growth of an optimal tumor dose challenge and promotes induction of tumor immunity. However, this drug cannot reverse the effect of iv injected tumor cells. Another drug with reported antisuppressor cell activity, cyclophosphamide (50 mg/kg), injected 1 day prior to challenge causes a transient inhibition of tumor growth. Injection of this drug on Day 7 does not have a significant effect by itself but, in combination with the Day-1 pretreatment, a significant inhibition of tumor growth by size and tumor incidence measurements is obtained. These results indicate that manipulation of immunity to transplantable fibrosarcomas in the chicken is possible with drugs acting on suppressor cells.