Ontogeny of B lymphocyte function. VIII. Failure of thymus cells from aged donors to induce the functional maturation of B lymphocytes from immature donors.

The role of thymus cells in mediating a step in the ontogeny of the capacity of the B cell population to produce a heterogeneous, high-affinity, primary, plaque-forming cell (PFC) response was further investigated. It was shown that the thymus acquires the capacity to facilitate this step in B cell differentiation between 3 and 4 weeks of age in C57BL/6 mice. This corresponds to the age at which te splenic B cell population of these mice naturally acquires the capacity to produce high-affinity PFC. The differentiation of the B cell population. It was further shown that regulates this step in the cells to facilitate the maturation of B cell population. It was further shown that the ability of thymus cells to facilitate the maturation of the B cell population decreases with age and is already markedly reduced in 30-week-old, long-lived, C57BL/6 mice. A qualitative or quantitative decrease in thymic function may thus be responsible for age-related changes in the function of the B cell population.