Immunoglobulin and cytokine production by neonatal lymphocytes.

Growth and differentiation of cord blood B cells were studied using T cell-depleted populations. In the absence of in vitro activation, cord blood B cells proliferated in response to cytokines including interleukin-2 (IL-2) and interleukin-4 (IL-4); anti-mu-stimulated cord B cells had a lesser response to IL-2 than adult cells. IgM synthesis by cord blood B cells was enhanced by interleukin-6 (IL-6) and decreased by IL-2. In cultures activated by Staphylococcus aureus Cowan I (SAC), cord blood B cells produced lesser increases in IgM than adult B cells regardless of the cytokine added. Cord blood B cells produced no IgG or IgA with any cytokine preparation with or without SAC activation. Supernatants of cord blood T cells pulse-stimulated with phytohaemagglutinin and phorbol myristate acetate contained less IL-2 and IL-6 and had less growth and differentiation activity than adult T cell supernatants. The results confirm a limited cord blood B cell response and also suggest a limitation in production of B cell stimulatory lymphokines by cord blood T cells.