[Structural features of immunoglobulin G from leukemic cattle]

Structural peculiarities of immunoglobulin G (IgG) in cattle with leukemia were studied using the method of dansyl-finger prints and proteolytic fragmentation with pepsin. It is stated that the protein from the blood of leukemic animals differs from the similar IgG subfraction of healthy animals in the amount of peptides: their number is 39 in sick animals, 41--in healthy ones. The studied protein is splitted into three fragments under the effect of pepsin. The molecular mass of F(ab1)2- and Fc1-fragments isolated from the hydrolyzate is 94 and 51 kDa, respectively. Fab-, Fc- and F(ab')2-, Fc'-fragments manifest a complete antigenic identity. The antibody activity is inherent only in the F(ab')2-fragment; it reacts positively in the precipitation test together with monospecific antiserum against IgG, typical of the malignant growth. This confirms a supposition that structural peculiarities of the protein typical of the malignant growth and isolated from the blood of cattle with leukemia depend on changes in the protein Fab-fragment.