Fc fragment from human IgG induces PGE2 secretion. II. Negative regulation in B cell differentiation

In humans, in vitro, Fc fragment of IgG at a low concentration induces plasma cell generation. However, Fc fragment at a high concentration induces PGE2 release of monocyte activation capable of inhibiting this differentiation. The levels of PGE2 in the supernatant culture from mononuclear cells from normal donors were examined as a function of culture duration and concentration of Fc, Fab fragments and IgG. Plasma cells containing intracytoplasmic Ig were demonstrated by immunofluorescence with a polyvalent antiserum to human immunoglobulin(s). PGE2 levels, from mononuclear cell cultures, were analyzed by the RIA test. The results indicated that the Fc fragments are able to induce PGE2 secretion. The maximal release of PGE2 occurs after 24 hr of culture; this level is proportionate to the quantity of Fc fragments introduced. The addition of indomethacin in the cell culture stimulated by a high concentration of Fc fragments reestablishes the percentage of plasma cells. These results suggest the regulatory role of Fc fragment by PGE2 secretion in B cell differentiation.