Modulation of antibody synthesis by an anti-tumour alga

An unicellular alga, Chlorella pyrenoidosa, which had been reported to protect C3H mice against sarcoma BP8, is shown, when injected in Freund's incomplete adjuvant, to modulate the antibody synthesis induced by immunization with a hapten-carrier complex. C. pyrenoidosa appeared to be able to initiate an antigenic competition between hapten and carrier determinants of the antigen molecule during antibody synthesis, and thus it could be speculated that C. pyrenoidosa modulates the immune response at the macrophage level.