Induction of in vitro Antigen-Specific Antibody Production against NIP-KLH in Nonadherent Cells Derived from Human Peripheral Blood Mononuclear Cells

A primary in vitro antibody response to 4-hydroxy-3-iodo-5-nitrophenylacetyl keyhole limpet hemocyanin (NIP-KLH) by plastic dish nonadherent human peripheral blood mononuclear cells (PBMC) was examined. Nonadherent cells of most donors produced an anti-NIP antibody when they were cultured with the antigen at a cell density of 2.5 × 106/ml in the presence of Staphylococcus aureus Cowan I (SAC) at a concentration of 0.003% for 5 days, washed and further cultured in the absence of the antigen and SAC for an additional 5 or 6 days. Nonadherent cells of ‘low-responders’ responded to NIP-KLH plus SAC and produced anti-NIP antibody when they were cultured with not only NIP-KLH plus SAC but also with the culture supernatant obtained on phytohemagglutinin (PHA) stimulation of a mixture of PBMC from 2 donors. Furthermore, it was found that the PHA supernatants could be very effectively substituted for by human recombinant interleukin-2.