PHYLOGENY OF IMMUNE RECOGNITION - FINE SPECIFICITY OF FISH IMMUNE REPERTOIRES TO CYTOCHROME-C

Using the structurally defined protein antigen cytochrome C, studies w ere conducted in an attempt to delineate the fine specificities of cha nnel catfish immune repertoires. We have previously reported that spec ies variants of cytochrome C were cross-stimulatory to peripheral bloo d leukocytes (PBL) from catfish immunized with the pigeon variant. Mol ecular database analyses revealed the existence of overlapping epitope s that appear to define the specificity of the immune response to a '' family'' of closely related antigens. To further explore these observa tions, studies were conducted to determine the contribution of peptide 81-104 to the immunogenicity of cytochrome C. Current data showed tha t peptide 81-104 and intact cytochrome C were stimulatory to PBL from fish previously immunized with the native molecule. In contrast, PBL f rom fish previously primed with the peptide 81-104 responded only to t he immunizing peptide as well as to some, but not all, variants of the peptide 81-104. The differences in the stimulatory capacities of the peptide variants appeared to correlate with amino acid substitutions a t various positions of the peptide and changes in their predicted seco ndary structures.