The requirement of thymus-derived cells for the immune response to trinitrophenylated syngeneic mouse red cells (TNP-MRC) was investigated. In three sets of experiments the following results were obtained: a) irradiated mice which were reconstituted with bone marrow cells alone showed a better anti-TNP response after injection with TNP-MRC than those reconstituted with both bone marrow cells and thymocytes. b) Anti-thymocyte serum augmented the mouse anti-TNP response to TNP-MRC. c) Nude thymusless mice showed a better anti-TNP response to TNP-MRC than their normal littermate controls. These results indicate that the anti-TNP response of mice to TNP-MRC does not require thymus-derived helper cells. Moreover, thymus-derived cells have a suppressive effect on the anti-TNP response.

No abstract

Mice primed with heavily trinitrophenylated sheep red cells (TNP128SRC) or glutaraldehyde-treated sheep red cells (G-SRC) developed an early helper function mediated by thymus-derived cells. Such mice were able to produce high secondary responses to both hapten and carrier after challenge 2 days after priming, with lightly trinitrophenylated SRC (TNP 0.14SRC). However, the primary response of the TNP 128SRC or G-SRC-primed mice were very low to undetectable, and their secondary responses were also low when the challenge antigen was administered 4 days after priming or later. Inhibitory humoral factor(s) which were induced in the primed animals appeared responsible for the decreased capacity of primed mice to mount a secondary response when challenged later than 2 days after priming. Transfer of spleen cells from TNP 128SRC-primed mice to sublethally irradiated recipients circumvents their exposure to inhibitory humoral factor(s) present in intact animals allowing them to react with challenge antigen. Enriched populations of T cells, but not B cells, were able to transfer this early immunologic memory to irradiated recipients. The theoretical and practical implications of these results are discussed.