Immunological studies in typhoid fever. II. Cell-mediated immune responses and lymphocyte subpopulations in patients with typhoid fever.

The development of the cell-mediated immune response (CMIR) to antigens prepared from Salmonella typhi was investigated in patients suffering from typhoid fever and in normal healthy subjects. The leucocyte migration inhibition test, blast transformation of lymphocytes and active rosette-forming cells were used for detecting CMIR. Peripheral blood lymphocytes were analysed for the numbers and proportions of B lymphocytes, T lymphocytes and their subpopulations with receptors for IgM (T micro) or IgG (T gamma) and cells with Fc receptors for IgG. These parameters were correlated with the duration and the severity of illness. The uncomplicated cases of typhoid fever were found to have an intact CMIR as compared to the complicated cases. The ratio of T lymphocyte subpopulations was grossly imbalanced in typhoid patients, the numbers of T lymphocytes and their subpopulations were further altered in he complicated cases as compared to uncomplicated cases. The present study demonstrates a depressed state of CMIR in complicated patients with typhoid fever. CMIR may thus emerge as the cardinal point for recovery in typhoid fever rather than the specific antibodies. The study further demonstrates that imbalance within the subsets of T lymphocytes may be responsible for the depressed state of CMIR in complicated cases of typhoid fever.