Role of specific delayed-type hypersensitivity in Pseudomonas aeruginosa-infected mice

The role of specific cell-mediated immunity was studied in mice injected in the hind footpad with viable Pseudomonas aeruginosa cells. The results reported here show that a state of specific delayed-type hypersensitivity, evaluated both as footpad swelling and as weight increase of popliteal lymph node, occurs in P. aeruginosa-infected mice. Furthermore, a T-cell-enriched spleen population from infected animals was able to transfer delayed hypersensitivity to normal recipients. However, identity at the major histocompatibility complex to transfer delayed hypersensitivity was required. Acquired cellular resistance was not transferred to normal recipients by immune T lymphocytes. On the contrary, mice receiving immune T cells showed an increase in the severity of the lesion caused by a viable challenge. The dichotomy between acquired cellular resistance and delayed hypersensitivity, and the possibility that T-cell reactivity to P. aeruginosa may be actively controlled, is discussed.