Immunoregulation of immunoglobulin production in normal infants and children.

Proportion of T cell subsets, spontaneous and PWM stimulated immunoglobulin production by peripheral blood lymphocytes and concanavalin A- (Con A) stimulated suppressor cell activity on immunoglobulin production by B cells was studied in 37 infants and children, to investigate changes of these parameters with age. Proportion of suppressor/cytotoxic (T8+) T lymphocytes was significantly lower in children below the age of 5 years, while there was no difference in proportion of total T lymphocytes (T3+) and helper/inducer (T4+) T cells. Spontaneous production and secretion of IgG and IgM by lymphocytes from children of all age groups was similar to that found in adults, but lymphocytes of children below the age of 10 years showed a low response to PWM stimulation. The activity of Con A-induced suppressor cells in inhibiting B cells producing immunoglobulins was almost absent in infancy, gradually increased during childhood and reached adult levels in teenagers. A significant association between the proportion of T8+ cells and Con A-induced suppression of B cell proliferation and a relationship between T4+ cells and spontaneous Ig production indicated the increasing maturity with respect to both number and function of peripheral blood lymphocyte subsets with advancing age.