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Antibody synthesis in anamnestic lymphoid cells, measured by incorporation of leucine-C(14) into specific antibody, was inhibited at moderate concentrations of actinomycin D. This was accompanied by marked inhibition of synthesis of RNA as measured by incorporation of H(3)-cytidine monophosphate. However, at low concentrations of actinomycin D, antibody synthesis was unaffected or even increased while RNA synthesis continued to be inhibited. The results obtained suggest that messenger RNA for antibody synthesis, either because it is relatively stable or present in excess, does not become a limiting factor until its synthesis is maximally inhibited. Puromycin, an inhibitor of amino acid coupling, abolished antibody synthesis in low concentration. 6-Mercaptopurine had no effect on the synthesis of antibody or RNA even at high concentration. The data obtained support the view that antibody synthesis follows pathways similar to those utilized for the formation of other types of proteins.

In an experimental arthritis induced by injection of bovine serum albumin or egg albumin into the joints of previously immunized animals, it has been demonstrated that the major portion of the radioactively labeled antigens injected was localized to avascular collagenous tissues in the joint, i.e., articular cartilage, menisci, and intra-articular ligaments. The antigens were partially eluted from the tissues with 5 M guanidine solution, but not with acid buffers or by 3 M magnesium chloride. The radioactive material eluted with guanidine was at least 80% precipitable by specific antisera. The radioactively labeled-inducing antigen was identified on the surface of articular collagenous tissues from arthritic joints by radioautography and immunofluorescence. Rabbit immunoglobulin and C3 were demonstrated in the same sites by immunofluorescence. The presence of specific antibody in collagenous tissues was demonstrated by the selective in vitro binding of (125)I-labeled-inducing antigen to menisci from arthritic joints of immunized animals. The evidence obtained indicates that in this model of chronic arthritis, the inducing antigen persists for long periods of time in the form of immune complexes in the surface layers of the intra-articular collagenous tissue. The antigen retained in this form may be responsible for the chronicity of the synovitis by serving as a direct stimulus for the maintenance of prolonged antibody synthesis in the synovium and by providing a source of complement-fixing antigen-antibody complexes for the mediation of joint inflammation.

Chick embryos were sacrificed at intervals after simultaneous injection of BAPN and proline-C(14), the collagen separated into neutral salt-extractable and residue fractions, and total hydroxyproline and hydroxyproline specific radioactivity determined in each fraction. Extractable collagen, measured as hydroxyproline, increased markedly and had a higher specific activity in BAPN-treated embryos than in corresponding controls. Hydroxyproline of the residue collagen in the treated animals, however, had a lower specific activity. When proline-C(14) was injected 24 hours prior to BAPN, the specific radioactivity of the soluble collagen of treated embryos was similar to that of controls, in spite of the fact that the specific activity of the residue fraction was higher than that of the soluble fraction at the time of BAPN administration. These results suggest that the increased amount of soluble collagen in lathyrism induced by administration of BAPN does not arise from the collagen insoluble prior to administration of the drug, but rather that BAPN acts by blocking the formation of mature collagen fibers, perhaps by preventing the formation of cross-linkages between alpha-collagen chains.