Antigenic Stimulation of Bone Marrow Colony Forming Cells II. PROPERTIES OF A SERUM FACTOR RESPONSIBLE FOR ANTIGENIC ENHANCEMENT OF COLONIES.

The enhancement effect of some antigens on in vitro colony formation by normal mouse bone marrow cells is mediated through a normal serum αmacroglobulin (αM) which is present in newborn animals and shows no immunological specificity. The proportion of antigen and αM affects colony enhancement, and it has also been shown that specific antibody successfully competes with αM for the antigen. It seems likely that antigen-αM complex acts directly on the colony forming cell, rather than indirectly through release of colony stimulating factor. The possible relevance of this phenomenon to immune induction and, to the effect of antigens in promoting irradiation survival is discussed. [ABSTRACT FROM AUTHOR]