Tetrahymena pyriformis recovers from antibody immobilisation by producing univalent antibody fragments

Abstract

MANY protozoa possess mechanisms by which they are able to recover from immobilisation by specific antibodies. Paramecia have been shown to shed their ciliar antigens in response to specific divalent antibodies. After shedding the antibody bound antigens the animals present new antigens of different specificity¹. It has been suggested that this modulation process also has a role in antigen variation in trypanosomes². While modulation of serotypes in Tetrahymena pyriformis is primarily provoked by temperature shifts or changes in culture conditions³, induction of modulation in response to antibody agglutination has been reported^4,5. Tetrahymena recovery from antibody provoked immobilisation has also been reported to occur by a nonspecific process not involving a change in serotype. Immobilised animals have been shown to secrete a substance which permits their recovery and protects animals of unrelated serotype from homologous anti-serum^6–8. We have further examined the way that Tetrahymena recover from antibody provoked immobilisation. This process, which we call fabulation, apparently involves the proteolytic cleavage of both bound and free immunoglobulin to produce univalent fragments which bind or remain bound to the ciliar antigens and protect the animals from further antibody treatment with no apparent effects on cell growth. The cleavage seems to be catalysed by both cell bound and secreted proteases.