Yes T cells, but three different T cells ( αβ , γδ and NK T cells), and also B‐1 cells mediate contact sensitivity

Transfer of contact sensitivity (CS) responses by immune lymphoid cells was the first finding that distinguished cellular from humoral immunity. CS has remained the most studied T cell reaction in vivo , and is the prototype for a variety of delayed‐type hypersensitivity (DTH) responses. DTH in essence is the recruitment of effector αβ‐T cells out of vessels into peripheral tissues. The T cells then are activated by antigen presenting cells to produce pro‐inflammatory cytokines. It has been assumed that the αβ‐T cells alone are responsible, but recent studies show that three other lymphocyte subsets are involved: CS‐inducing NK T cells, CS‐initiating B‐1 cells, and CS‐assisting γδ‐T cells. Therefore, the effector αβ‐T cells are essential, but cannot be recruited into the tissues without the local action of IgM antibodies produced by B‐1 cells rapidly (1 day) post‐immunization. The IgM complexes with the challenge antigen to locally activate complement to lead to vascular activation required for T cell recruitment. This process occurs early (1‐2 hours) in the elicitation phase, and is called CS‐initiation. The essential CS‐inducing NK T cells activate the B‐1 cells by producing IL‐4 rapidly (1 hour) after immunization, and γδ‐T cells assist the local inflammatory function of the recruited CS‐effector αβ‐T cells. Thus, four lymphocyte subsets are required for elicitation of responses: CS‐inducing NK T cells, CS‐initiating B‐1 cells, CS‐assisting γδ‐T cells, and finally the CS‐effector αβ‐T cells. Three of these four cell types are present in the immune lymphoid cell population that adoptively transfers CS: B‐1 cells, γδ‐T cells, and the αβ‐T cells.