Regression of v-src DNA-induced sarcomas is under host genetic control

Brief review of the chicken Major Histocompatibility Complex: the genes, their distribution on chromosome 16, and their contributions to disease resistance

Nearly all genes presently mapped to chicken chromosome 16 (GGA 16) have either a demonstrated role in immune responses or are considered to serve in immunity by reason of sequence homology with immune system genes defined in other species. The genes are best described in regional units. Among these, the best known is the polymorphic major histocompatibility complex-B (MHC-B) region containing genes for classical peptide antigen presentation. Nearby MHC-B is a small region containing two CD1 genes, which encode molecules known to bind lipid antigens and which will likely be found in chickens to present lipids to specialized T cells, as occurs with CD1 molecules in other species. Another region is the MHC-Y region, separated from MHC-B by an intervening region of tandem repeats. Like MHC-B, MHC-Y is polymorphic. It contains specialized class I and class II genes and c-type lectin-like genes. Yet another region, separated from MHC-Y by the single nucleolar organizing region (NOR) in the chicken genome, contains olfactory receptor genes and scavenger receptor genes, which are also thought to contribute to immunity. The structure, distribution, linkages and patterns of polymorphism in these regions, suggest GGA 16 evolves as a microchromosome devoted to immune defense. Many GGA 16 genes are polymorphic and polygenic. At the moment most disease associations are at the haplotype level. Roles of individual MHC genes in disease resistance are documented in only a very few instances. Provided suitable experimental stocks persist, the availability of increasingly detailed maps of GGA 16 genes combined with new means for detecting genetic variability will lead to investigations defining the contributions of individual loci and more applications for immunogenetics in breeding healthy poultry.

Nutritional modulation of immune function in broilers

Collaborative research efforts across disciplines typically result in more insight toward the hypothesis being tested due to the omnibus nature of the projects. For example, nutritional experiments evaluating a nutrient response will benefit greatly by incorporating biochemical, physiological, and immunological endpoints for measurement. Clearly, commercial poultry producers do not have the luxury of focusing on specific disciplines when field problems occur. Hence, in practice interplay exists among nutrition, genetics, management, and diseases. Dietary composition impacts immune function of the chicken. As research in the area of nutritional immunology has increased, it is becoming apparent that nutrient needs for immunity do not coincide with those for growth or skeletal tissue accretion. This review is not a comprehensive assessment of nutrient needs for immunity in the chicken. Rather, this review is concerned with nutritional modulation of immunity in broilers that offers insight for nutritionists and researchers to implement nutritional regimens to reduce the severity of disease and to test or validate nutritional regimens that heighten immunity. Nutritional modulation of the hen diet and in ovo nutrient modulation to improve chick immunity and disease resistance are discussed.

Sequence variation in the src gene product affects metastasis formation: the central, but not exclusive, role of the tumor immune response

Sequence variation in the src gene product could, in principle, influence metastasis formation through either of 2 effects: an alteration in tumor antigenicity or a non-immune-mediated change in one or more src-associated functions. Our present results establish that both mechanisms underlie the difference in relative levels of metastasis formation induced by the v-src vs. the c-src(527) oncogene. A point that emerges from this analysis is the segregation, within a chicken line genotypically uniform at the major histocompatibility (B) complex (MHC), of a phenotype defined by strong resistance to secondary v-src-induced tumor challenge. The pattern of segregation is consonant with the possibility that a gene unlinked to the MHC governs immune response levels to v-src-encoded tumor antigen.

Tumor cells induced by the v-src oncogene are heterogeneous for expression of markers of mesenchyme differentiation

The observation that v-src-induced tumors contain tumor cells of differing morphology, notably fibroblastoid or polygonal, raised the question as to whether the tumor cells are also heterogeneous with respect to expression of markers of cellular differentiation. Of the markers tested here, consistent reactivity for tumor tissue was noted only for antibody probes reactive to muscle actin (HHF35, alpha sm-1) or to procollagen type I (SP1. D8); for any given tumor, whether induced by v-src DNA or by Rous sarcoma virus, each of these markers was found only in a subpopulation of tumor cells. The observation of marker heterogeneity in the one v-src DNA-induced tumor examined here that typed as monoclonal suggests that v-src-induced transformation is consonant with a degree of plasticity in the phenotypes of the clonal progeny of a single transformant.

Major histocompatibility (B) complex control of the growth pattern of v-src DNA-induced primary tumors

Observations that the major histocompatibility (B) complex is a determinant of the growth pattern of Rous sarcoma virus (RSV)-induced tumors raised the question as to whether control is exerted at the level of a v-src-determined, i.e., transformation-specific, function. To investigate this point, the tumor size scores and tumor profile indices of v-src-induced tumors were compared in two lines of chickens congenic for B complex genotypes. The finding that the growth patterns of tumors, induced by v-src DNA inoculation at 6 weeks posthatch, differ in these two lines establishes that the B complex exerts control over tumor growth at the level of a v-src-determined function. The potential importance of this control, in terms of the naturally occurring case of an avian sarcoma virus infection, is suggested by the observation that the patterns of tumor growth in a given congenic line are similar whether the tumors are induced by v-src DNA or by RSV.

Possible functions of a new genetic marker in central nervous system: the sulfated glycoprotein-2 (SGP-2)

This brief review discusses the recent characterization in the brain of a gene coding for a protein that may be involved in programmed cell death and/or brain plasticity. We will term it sulfated glycoprotein-2 (SGP-2), the name corresponding to the first cDNA characterized. Recent studies have demonstrated the overexpression of this sulfated glycoprotein in various CNS disorders, such as certain gliomas, Alzheimer's disease and epilepsy, as well as after experimental brain injury in animals where different cell types were undergoing tissue remodelling or cell death. In peripheral tissues, SGP-2 gene expression has been found to be strikingly increased following experimental manipulations in which cells of injured tissues were undergoing programmed cell death or apoptosis. The results reported thus far are intriguing and suggest the possible involvement of SGP-2 in apoptotic mechanisms as well as its interaction with components of the immune system possibly associated with cell death in neurodegenerative disorders.

Wounding acts as a tumor promoter in chickens inoculated with avian sarcoma virus 17

Avian sarcoma virus 17 (ASV17) is an acutely transforming retrovirus which carries the oncogene v-jun. The virus induces fibrosarcomas in chickens at the site of inoculation. Here we describe wound-related tumor formation in 77% of chickens inoculated with ASV17 in one wing and wounded by metal clip insertion in the opposite wing. Tumors from both wound-related and inoculation-related sites were histologically diagnosed as fibrosarcomas. Tissues cultured from both tumor sites produced infectious virus in culture and expressed high levels of the v-Jun oncoprotein detectable by immunofluorescent staining. By varying the time of wounding relative to virus inoculation we defined the early stages of wound healing (2-7 days postinoculation) as favoring wound-related tumor formation. Three other acutely transforming retroviruses containing oncogenes coding for nonreceptor protein tyrosine kinases (v-src, v-yes, and v-fps), inoculated in the same manner, induced wound-related tumors in all cases. We conclude that in chickens, ASV17 collaborates with wound healing to promote tumorigenesis by a process which may relate either to a biochemical function of Jun or to a more general, shared characteristic of transforming retroviruses.

Tumor immunity generated in the course of regression of v-src-induced sarcomas

Previous studies have indicated that the regression versus progression of v-src-DNA-induced sarcomas is dependent on chicken line. As a first step in analyzing the role of tumor immunity as a determinant of this line dependence, experiments were undertaken to ascertain whether an antisarcoma immune response is generated in the course of sarcoma growth in TK chickens, a regressor line. To assay for this response, test TK chickens in which v-src-induced wing web sarcomas had regressed, as well as control TK chickens that had not been exposed to v-src, were challenged in protocols known to yield v-src-dependent sarcoma formation and monitored for challenge sarcoma growth. Compared with the control chickens, the test chickens showed a significant resistance to the sarcomagenic challenge. These results raise the possibility that the antisarcoma response that is inducible in regressor lines, as demonstrated here in terms of a protective effect against a subsequent sarcomagenic challenge, may also underlie the regression of v-src-induced primary sarcomas.