Influenza: response of T-cell lymphopenia to thymosin.

Eighteen volunteers in tow study groups were inoculated with influenza A (H3N2) and their peripheral blood T, B and null cells enumerated at subsequent intervals. Infection with wild-type virus or with a live, attenuated virus vaccine markedly reduced the proportion and absolute number of T-cell rosettes 24 hours after inoculation. T-Cell depression preceded the onset of clinical illness in symptomatic subjects, continued during illness, and returned to normal with recovery. T-cell lymphopenia was most pronounced in volunteers infected with wild-type virus and was accompanied by an increase in null cells. Lymphocytes from six wild-virus recipients with T-cell leukopenia were incubated in vitro with a calfthymus extract (thymosin), significantly increasing the percentage of T rosettes in all six subjects (P less than 0.0001). These data indicate that influenza is accompanied by pronounced quantitative and functional changes in T cells.