Influence of Thymus Genotype on Acquisition of Responsiveness in Delayed‐type Hypersensitivity

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Abstract
Antigen-pulsed macrophages (Mph) could sensitize syngeneic mice for delayed-type hypersensitivity (DTH) and also elicit sensitivity from mice sensitized to antigen in adjuvant provided these were syngeneic or semi-allogeneic to the strain providing the Mph. Sensitivity could not be elicited with antigen-pulsed allogeneic Mph. Antigen-pulsed Mph from low-responder (LR) strains could not sensitize LR mice nor F1 hybrids between responder (R) and LR strains. Normal F1 mice could he sensitized to respond to antigen presented on Mph of either parental type (i.e. P1 or P2): if, however, they were sensitized to antigen on P1 Mph. DTH transfer was restricted to naive P1 mice, not to P2 (restriction imposed by priming). F1 T cells derived from stem cells differentiating in a P1 thymus graft could he sensitized but could transfer sensitivity only to naive P1 mice, not to P2 (restriction imposed in thymus). When an antigen under Ir gene control was used, LR derived T cells differentiating in an (R×LR)F1 thymus could be sensitized but only if antigen was presented on (R×LR)F1 Mph not on LR Mph. Totally allogeneic chimaeras could be sensitized but only if given antigen in association with the appropriate Mph. These findings suggest that restriction of T cell activities can be imposed as a result of priming in some cases and as a result of differentiation within the thymus in others. LR strains appear to have a lesion at the level of antigen presentation by Mph; whether they also have a defect at the level of generation of T cell repertoire cannot he determined from the present investigations.

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