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

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."

Avian peritoneal exudate cells: a comparison of stimulation protocols

The influence of different stimulation protocols on the induction of peritoneal exudate cells (PECs) and adherent cells, and on the percentage of different adherent cell types was examined in the chicken and Japanese quail. The results suggest that different protocols may be selected to maximize isolation of specific PEC populations for immunological studies. In the chicken, starch, peptone, glycogen, and Sephadex G-40 were all equally effective and superior to saline in generating PECs. While a single injection of Sephadex produced the highest yield of adherent cells with a maximum percentage of macrophages, repeated injections of Sephadex led to dramatic increases in non-adherent PECs (lymphocytes). In contrast, a single injection of starch was optimum for generating non-macrophage adherent cells (primarily heterophils). Since responses of the Japanese quail to stimulation with starch and saline were similar to those observed for the chicken, it is suggested that these protocols may be generally applicable for use with avian species.

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.