Immunity to Trichinella spiralis. I. Transfer of resistance by two classes of lymphocytes.

Rats can be solidly immunized against Trichinella spiralis by a series of methyridine-terminated oral infections with T. spiralis larvae. Injections of thoracic duct lymphocytes (TDL) obtained from such animals can protect normal rats against a Trichinella challenge. The protective cells belong to two populations which differ with respect to their adherence to affinity columns prepared with rabbit antibody to rat F(ab')2. Immune lymphocytes in the column-adherent B cell fraction are inhibited by vinblastine, whereas those in the non-adherent, T cell fraction are resistant to this drug. The above observations suggest that acquired resistance to T. spiralis is mediated by two classes of lymphocytes: B cells which are delivered to the thoracic duct and hence to the blood while still in active cycle, and T cells which have a potentially long life-span and presumably belong to a pool of recirculating small lymphocytes.