Genetic polymorphism of a serum euglobulin of chickens which binds to antigen-antibody complexes

Mapping of the chicken immunoglobulin heavy-chain constant region gene locus reveals an inverted alpha gene upstream of a condensed upsilon gene

Chicken antibodies are increasingly being used as diagnostic and therapeutic tools. As only the genomic organization of the micro encoding gene was previously known, we analysed the chicken immunoglobulin Y (IgY) and IgA (upsilon and alpha chain) immunoglobulin heavy-chain constant region (IGHC) genes and the organization of the chicken IGHC locus. The alpha gene is encoded by four separate exons, whereas, surprisingly, there is no intervening DNA sequence between the CH1 and CH2 domains of the IgY heavy chain, which is thus encoded by three exons separated by two introns. DNA sequence analysis shows that the exon boundaries of the chicken IGHC genes are not consistent with published domain borders. Furthermore, differences in DNA sequence confirm the existence of IgY, IgA and IgM allotypes in chickens. Finally, our results show that the IGHC genes of chicken (IgY, IgA and IgM) are all colocated on chromosome E18C15W15, where the alpha gene is located upstream of the upsilon gene in an inverted transcriptional orientation. The distances between the mu and alpha genes and the alpha and upsilon genes are about 18 and 15 kilobases, respectively, and thus, the size of the whole chicken IGHC locus is approximately 67 kilobases.

Immunological tolerance in the chicken. III. Partial physiochemical characterization of two suppressive fractions from serum of chickens tolerant to bovine serum albumin

Two soluble non-specific suppressive factors were isolated by gel chromatography from the serum of chickens tolerant to bovine serum albumin (BSA). Fraction I was found by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) to contain five proteins with mol. wts from 200,000 to 900,000 unreduced and six proteins that ranged from 70,000 to 180,000 when reduced. The composition was primarily protein, with a small amount of carbohydrate and lipid. One component was identified as IgM, one as a lipoprotein. The others remain unidentified. No evidence of the tolerogen, BSA, was found. The second factor, fraction III of both tolerant and normal serum, was found by SDS-PAGE to have two proteins with mol. wts of 54,000 and 78,000 in the unreduced form and contained a very small amount of protein, a large amount of carbohydrate, and no detectable lipid. Normal fraction III had two proteins with mol wts of 54,000 and 65,000 when reduced, whereas reduction did not affect tolerant fraction III. A soluble suppressive factor, secreted by cultured adherent cells of tolerant chickens, was found to be comparable to fraction III in molecular weight. Comparison of these results with those of other reported suppressive factors is made and possible identities of the suppressive components of fractions I and II are discussed.

Haemagglutination-enhancing factor protein in chicken serum. I. Purification of an active protein and production of a monospecific antiserum against it

The haemagglutinating activity of the IgG fraction of chicken alloantibodies is greatly enhanced by the addition of normal chicken serum. The effect is due to a macromolecular beta-globulin, which has been purified by salt precipitation, gel filtration, and ion-exchange chromatography. Immunization of rabbits with the purified product gave a monospecific antiserum against the haemagglutination-enhancing factor (HEF) protein. By means of this rabbit antiserum it is shown that HEF is co-precipitated with antigen-antibody complexes. This indicates that HEF exerts its effect by binding to chicken IgG antibody after the latter has reacted with antigen.