Abstract
The effect of rabbit antiserum to heat-aggregated mouse immunoglobulins (AAS) upon rosette formation by mouse spleen cells was examined before and after immunization with sheep erythrocytes. Pretreatment with AAS of spleen cells obtained during the first five days after immunization resulted in up to 707. reduction in detectable rosette-forming cells (RFC). RFC sensitive to AAS treatment did not contain 4tH antigen and carried Ig receptors. Spontaneous RFC from normal mice, just like those observed later than five days after immunization were not inhibited by AAS. The data obtained are considered as indication that aggregated Ig appearing on B cells during the initial period following primary immunization are, probably, immune complexes which serve as antigen-binding receptors.