INHIBITION BY C3 FRAGMENTS OF C3-DEPENDENT ROSETTE FORMATION AND ANTIGEN-INDUCED LYMPHOCYTE TRANSFORMATION.

The interaction in vitro between human lymphocytes and fixed C3 was inhibited by fluid phase C3b and C3c prepared by trypsinization of purified human C3. These C3 fragments suppressed in vitro transformation of human lymphocytes by specific antigens, PPD and Candida albicans somatic antigen, but not by phytohaemagglutinin, a non-specific mitogen. These observations indicate the form of C3 which interacts with complement receptor lymphocytes and suggest that this interaction may play a part in lymphocyte activation by antigen. [ABSTRACT FROM AUTHOR]