Delayed‐Type Hypersensitivity in the Mouse

Delayed‐type hypersensitivity (DTH) to Salmonella polymerized flagellin (POL) was transferred to normal and lethally irradiated CBA mice by POL‐activated thymus‐derived (T) cells or by lymphoid cells rich in T cells from POL‐primed donors, but not by POL‐activated bone marrow‐derived (B) cells or by serum from POL‐primed donors. It was therefore concluded that T cells play a key role in the initiation of DTH reactions. T cells activated by POL of one specificity were equally able to transfer DTH to POL of the same or of another specificity. DTH to haemocyanin (HCY) (Jasus lalandii) was transferred only by HCY‐activated T cells. Two interpretations of these findings are discussed: 1) that T cells may be less restricted in specificity than B cells, and 2) that T cells recognize a common antigenic determinant (carrier determinant) on the polymerized flagellins of Salmonella spp, which is not recognized by B cells.