Evidence for a soluble lymphocyte factor in the transplacental transmission of T-lymphocyte responses to Mycobacterium leprae

Abstract

ANTIGENS introduced to the human foetus have been considered as “self” and thus not to provoke an immune response¹. But, no sudden changes in the immune mechanisms seem to coincide with birth, and the development of adult immune responses is gradual. Moreover, in sheep, antigens can give rise to more or less mature immune responses in the foetus^2,3, dependent on the stage of gestation. The nature of transmission of these immune responses from mother to foetus remains unclear. Brody et al.⁴ demonstrated in humans that T-lymphocyte sensitisation could be transmitted from mother to foetus and considered this was due to transplacental passage of antigen. Field and Caspary⁵ showed that cell-mediated responses can be induced in the foetus, but thought that either maternal lymphocytes or some subcellular lymphocyte factor crossed the placenta to sensitise the foetal lymphocytes. We have tested ten randomly selected normal mothers and their babies at parturition for evidence of sensitisation to antigens of Mycobacterium leprae. We found that when the mothers showed sensitisation their babies did too: the children of unsensitised mothers were not sensitised. We consider the likeliest explanation for our findings is the transplacental passage of a soluble lymphocyte factor.