T-cell depletion and in vitro thymosin inducibility in asthmatic children.

Thirty asthmatic children were compared with an equal number of age-matched healthy children. The mean peripheral blood T-lymphocyte level without foetal calf serum was lower in the asthmatic group (mean 970/mm3, as against 1740/mm3; P less than 0.0001), but this difference was abolished by adding foetal calf serum or thymosin, thus explaining how quite severe T-cell deficiency can be missed by widely used methods. The degree of eosinophilia and the degree of elevation of the plasma IgE level in the asthmatic patients were positively correlated. Positive correlations were also shown between the degree of severity of the asthma, the degree of eosinophilia and the degree of elevation of the plasma IgE level, but not the degree of depression of the T-cell numbers. If this T-cell deficiency reflects an inadequate suppression of IgE responses, a clinical trial of thymosin appears to be warranted.