[Presence of antigenic determinants in mRNA-containing RNP particles of immune B-lymphocytes].

An iodinated erythrocyte antigen isolated from sheep erythrocytes (125I-EAG) was injected to the BALB/c or CBA mice in a single dose of 20-25 mkg as for protein. The antigen determinants were detected by incorporation of a radioactive label into spleen B-lymphocytes on the 1sh-5th post-immunization days. It was shown that the T-cells contain no label and that 2/3 of the radioactivity of B-lymphocyte suspension of the 125I-EAG-immunized mice are detected in the cell nuclei within mRNP. During electrophoresis of the particles in 2,5% polyacrylamide gel nuclear mRNP isolated from B-lymphocytes of mice immunized with cold EAG are adsorbed by an immunoadsorbent containing antibodies against sheep erythrocytes. Fractionation of 125I-cytoplasmic extract obtained from 125I-EAG-immunized mouse B-lymphocytes in sucrose gradient revealed that the radioactive label was detected in the same two regions of the sucrose gradient, which is occupied by light RNP complexes containing mRNA and polyribosomes. Under experimental conditions allowing to detect the transitions of mRNP complexes into polyribosomes, a shift of the 125I-labelled material (probably together with the RNP particles) towards polyribosomes was observed. Thus, the antigen determinants are detected as part of nuclear and cytoplasmic mRNP of B-lymphocytes during the whole cycle of the primary immune response and are detected within the composition of cytoplasmic mRNP during the immunoglobulin polypeptide chain synthesis.