Expression of an onco-developmental antegen among avian species

Demonstration of chicken fetal antigen (CFA) on normal splenic lymphocytes, Marek's disease lymphoblastoid cell lines and other neoplasms

Chicken fetal antigen (CFA) was detected on normal splenic lymphocytes and a direct relationship was observed between the percentage of CFA-positive cells and the age of the donor. The fetal antigen was also detected on lymphoblastoid tumor cells and cell lines induced by known avian oncogenic viruses (Marek's disease virus and avian leukosis virus), and on spontaneously occurring adenocarcinoma cells. The fetal antigen appears to be distinct from Marek's disease tumor-associated surface antigen.

Chick embryonic erythrocyte antigen--tissues sharing expression

There is an antigenic glycoprotein (Mr 48 kD) present on the surfaces of erythrocytes of embryonic and young chickens that cannot be detected on the circulating erythrocytes in adult birds. This antigen, generally defined by this differential expression, has been thought to be associated with the maturation of hematopoietic tissues. We now present evidence, based on the use of a monoclonal antibody, maEE1, and the characteristic pattern of this glycoprotein on two-dimensional (2D) gels, that this antigen, which we have named chickEE, is expressed in a number of other embryonic and adult tissues. Immunofluorescent labeling of cryosections and flow-cytometric analysis of cells labeled with maEE1 have revealed the presence of chickEE in the retina (present in all layers), in muscle tissues (present in the endomysium and within the vascular endothelium), in the liver (especially evident on the lateral surface of hepatocytes and within the sinusoids), on epithelia such as the gut and kidney tubule epithelium and within lymphoid organs (present on bursacytes, splenocytes, thymocytes and peripheral leukocytes, and again within the endothelium) of young and adult animals. The 2D gel patterns of chickEE derived from embryonic tissues (retina, hind limb, thymus and bursa) and the adult tissues (retina and spleen) are very similar to that of the embryonic erythrocyte. Thus, the extended reactivity of the monoclonal antibody to chickEE, maEE1, with additional tissues is, in at least the tissues examined, based on the presence of the chickEE glycoprotein and not on incidental cross-reactivity. The evidence presented in this paper for the widely-shared expression of chickEE antigen makes it necessary to reconsider the function of this component of the cell surface.

Chicken developmental antigens: analysis of erythroid populations with monoclonal antibodies

Fusions were performed between the mouse PAI myeloma cell line and spleen cells from Balb/c mice immunized with intact erythrocytes from 1-day Cornell K-strain White Leghorn chickens. Following single cell cloning, four hybridoma clones were found to secrete erythroid specific monoclonal antibodies. Based on its pattern of reactivity, the antibody (IgG2a, kappa) secreted by clone 10C6 detects a specific avian oncodevelopmental antigen associated with the hematopoietic system: chicken fetal antigen (CFA). Two other clones, designated as 3F12 and 4C2, produced antibodies (IgM, kappa) that recognize another avian developmental antigen: chicken adult antigen (CAA). A fourth clone, 9F9, produced an antibody (IgM, kappa) that reacts with all peripheral erythrocytes from both Japanese quail and chicken regardless of age. Clone 10C6 antibody apparently detects an erythrocyte specific (ES) determinant of CFA associated with determinant #8 while antibodies of clones 3F12 and 4C2 recognize a chicken specific determinant of CAA. Analysis by complement mediated microcytotoxicity indicated that the epitopes detected by 10C6 vs 3F12 and 4C2 antibodies were expressed on erythrocytes in a reciprocal fashion during development. Furthermore, strain variations in the incidence of erythrocytes carrying these epitopes were observed. The usefulness of these monoclonal antibodies for the study of erythroid populations is discussed.

Molecular characterization of fetal antigens on red blood cells of chickens, Japanese quail, and quail-chicken hybrids

The molecular nature of chicken fetal antigen (CFA) and quail fetal antigen (QFA) was studied on embryonic red blood cells (RBCs) of the chicken, the Japanese quail, and the quail-chicken hybrid. Specific immunoprecipitation of radiolabeled membrane proteins followed by electrophoretic separation and autoradiography were used to identify the protein molecules carrying these fetal antigens. CFA was found on molecules of 24, 50, 88, 99, 130, 170, and 220 kd (kilodaltons) in the chicken and hybrid and on molecules of 24, 50, 99, and 170 kd in the Japanese quail. Similarly, quail fetal antigen was associated with 24-, 50-, 99-, and 170-kd molecules in the quail and hybrid and was not detected in the chicken. Partial proteolytic digestion of the 50- and 170-kd molecules isolated from RBCs of all sources showed remarkably similar peptide patterns. Likewise, two-dimensional separation of the CFA-positive and QFA-positive 50-kd molecules from quail RBCs revealed a similar pattern of at least nine isomorphic variants. Sequential depletions of quail embryonic RBC extracts with either anti-CFA or anti-QFA followed by immune precipitation with the reciprocal antiserum suggested that most of the cell surface proteins carrying QFA also have CFA on the same molecules. It is suggested that specific glycosylations of a variety of distinct molecular weight proteins determines the antigenic phenotype characterized as "fetal antigens."

Hematopoietic differentiation cell surface antigen switching in the bone marrow of different aged chickens

Immune cytolysis and immunofluorescence were used to examine chicken fetal antigen CFA) and chicken adult antigen (CAA) expression on the differentiation/maturation series of definitive erythroid cells obtained from the bone marrow of different aged chickens. We found that erythroid cells undergo changes in CFA/CAA antigenic expression dependent on their differentiation/maturation stages as well as the developmental age of the chicken. All differentiation/maturation stages of erythroid cells in the bone marrow of 12 and 18-day-old embryos express CFA only. Erythroblasts obtained from 7-day post-hatched chickens express either CFA or CAA. All three CFA/CAA phenotypes (i.e., CFA, CAA, and CFA + CAA) are observed in subsequent maturation stages, but only the CFA + CAA phenotype is observed in mature erythroid cells in the bone marrow of 7-day post-hatched chickens. Erythroblasts from 62 day post-hatched chickens exhibit all three CFA/CAA phenotypes. Cells in the subsequent maturation stages express various CFA, CAA, or CFA + CAA phenotypes resulting in a majority of the mature erythrocytes expressing both CFA and CAA, and a small population of mature erythrocytes expressing CAA only. Erythroblasts from adult chickens express both CFA and CAA; however, CFA is lost during erythroid maturation resulting in mature erythrocytes which express CAA only. These studies indicate that both the erythroid differentiation/ maturation stage and the developmental age of the chicken influence CFA and CAA antigenic expression on erythroid cells undergoing cellular differentiation/maturation in the bone marrow.

Quail fetal antigen (QFA): identification and comparison with chicken fetal antigen

Quail fetal antigen (QFA), an analogous hematopoietic antigen to chicken fetal antigen (CFA), was identified and shown to be a developmental antigen on the blood cells of Japanese quail and other avian species. Rabbit antiserum against 14-day embryonic quail red blood cells (RBCs) was specifically adsorbed to achieve fetal specificity and to eliminate any cross reactivity with the CFA system. Complement-mediated microcytotoxicity and hemagglutination assays were used to detect the presence of QFA on hematopoietic cells. QFA was found on 100% of the peripheral RBCs from 10-day quail embryos but incidence of the antigen gradually declined with increasing development. Complete loss of QFA from RBCs occurred just prior to sexual maturation between 31 and 42 days of age. No qualitative differences in erythroid expression of QFA were observed during development; however, RBCs from both embryonic duck and interspecific quail- chicken hybrids reacted with R-anti QFA. Like CFA, quail fetal antigen was associated with lymphocytes, particularly those from primary lymphoid organs. Similarities in the developmentally controlled tissue distribution of QFA and CFA suggest that developmental hematopoietic antigens are a common feature of avian species and are useful cell surface markers for studies of development and differentiation.

Characterization of a genetically segregating determinant of chicken fetal antigen by a new hapten inhibition of microcytotoxicity (HIM) assay

The immunodominant structure of a chicken fetal antigen (CFA) determinant was investigated using a new hapten inhibition of microcytotoxicity (HIM) assay. This HIM assay employing avian erythrocytes was shown to be a highly sensitive, economical technique and was verified in a separate experiment using bovine serum albumin (BSA) coupled to Japanese quail peripheral red blood cells (QPRBCs). Inhibition of microcytotoxicity was measured following preincubation of 1 microliter of specific antiserum with 1 microliter of antigen solution. A concentration of 21.1 nM BSA was found to produce effective (50%) inhibition of microcytotoxicity of BSA-coated QPRBCs. The percentage cytotoxicity was determined by estimating the proportion of intact RBCs to free nuclei using an inverted microscope. Staining of the reaction mixtures was not required for scoring. Application of this technique for the characterization of immunodominant structures was demonstrated by the analysis of a CFA determinant known to exhibit both developmental expression and genetic segregation. R-anti-CFA-10 was effectively inhibited only by D-galactose (35.5 mM) and the galactose-containing sugars lactose (28.2 mM), raffinose (29.9 mM), and stachyose (39.8 mM). Implications of the carbohydrate nature of CFA are discussed.

Chicken fetal antigen: association with lymphoid development and differentiation

Rabbit antisera capable of detecting chicken fetal antigen (CFA) was prepared against 1-day chick red blood cells (RBCs) and made specific by exhaustive adsorption with adult chicken peripheral RBCs (PRBCs) from the same strain. Microcytotoxicity was used to study the incidence of CFA on lymphocytes obtained from several organs at different developmental stages in the chicken. Lymphocyte-associated CFA (LA-CFA) determinants and erythrocyte-specific CFA (ES-CFA) determinants were distinguished through the use of adsorption analysis. The high incidence of CFA-positive lymphocytes found in the fetal bursa and thymus was not equaled in the peripheral organs of the spleen, cecal tonsils, and gland of Harder. CFA expression on adult lymphocytes was restricted to the thymus and peripheral blood. It is suggested that these cells may represent a subpopulation of T lymphocytes. Adult spleen, cecal tonsils, and gland of Harder were virtually devoid of CFA-bearing lymphocytes. At fetal developmental stages when greater than 94% of the bursal B cells were CFA-positive, few, if any, of the highly differentiated Harderian B cells possessed CFA. It is suggested that LA-CFA expression is dependent upon B cell differentiation and/or the bursa (central) vs gland of Harder (peripheral) microenvironment. The pattern of CFA expression on bursacytes is discussed in light of the properties of age resistance and bursal-dependent target cells associated with virally induced lymphoid leukosis.

Developmental changes in the presence of specific chicken fetal-leukemic antigen determinants in the chicken, Japanese quail, and the interspecific hybrid

The pattern and timing of expression of chicken fetal-leukemic antigen (CFA) on peripheral red blood cells (RBCs) is reported for specific periods of postembryonic development in chickens, Japanese quail, and quail-chicken hybrids. Individual CFA determinants were lost from the peripheral RBCs of chickens and hybrids at specific times of development. The sequential pattern of phasing in these sources suggests that at least some of the CFA determinants may be expressed independently on the cell surface. In addition, the time of phasing for each determinant may represent a developmentally-controlled change in the internal or external environment of the differentiating erythrocyte. In contrast, three CFA determinants appeared to be lost simultaneously, or over a short period of time, from the RBCs of Japanese quail. This phasing event appears to occur approximately one week prior to the onset of egg production. In the interspecific hybrid, the same three CFA determinants appeared to be independent with regard to the periods in which they were expressed on peripheral RBCs.

Chicken fetal antigen expression on the definitive erythroid maturation series in the bone marrow of the adult chicken

Chicken fetal antigen (CFA) describes a membrane developmental antigen system present on embryonic and fetal erythroid cells that is present during development, but is absent on erythrocytes of mature chickens. In this study, CFA was detected by indirect immunofluorescence and correlated with six stages of morphological maturation of erythroid cells. All cells in the erythroid series through the late polychromatic erythrocyte (reticulocyte) stage were found to possess CFA. Fluorescent intensity and staining patterns of the definitive erythroid series demonstrated CFA concentration increase and distribution pattern change throughout erythroid maturation.

Genetic regulation of CFA expression in interspecific avian hybrids and somatic cell hybrids

Chicken fetal-leukemic antigen (CFA) is an oncodevelopmental antigen present on embryonic and neonatal chicken peripheral red blood cells (RBCs) but is not restricted to fetal stages of development in other avian species. Crosses between white Leghorn chickens and Japanese quail resulted in adult hybrids whose peripheral RBCs were positive for CFA. Of the four CFA determinants normally found in adult quail RBCs, only two were present on quail-chicken hybrid RBCs. Adult quail--chicken hybrid RBCs also possessed on CFA determinant associated with early development in both quail and chicken and one chicken-specific CFA determinant. Evidence is presented for the possible association of CFA-positive adult peripheral RBCs and the level of circulating reticulocytes. Crosses between pheasant and turkey (both with CFA-positive adult RBCs) resulted in hybrid adult RBCs expressing only a portion of the parental CFA determinants. Through the formation of somatic cell hybrids between adult chicken and embryonic Japanese quail RBCs, it was possible to induce the appearance of CFA determinants normally restricted to embryonic chicken RBCs. Approximately 50% of the hybrid cells showed reexpression of CFA, and this induction was both time and temperature dependent. Hybridization between RBCs of adult chicken and those of either adult Japanese quail or adult turkey failed to elicit the reexpression of chicken-specific CFA.