Basophil production III: relation of histamine to guinea pig basophil growth in vitro

Histamine has been measured by an isotopic enzyme conversion assay in guinea pig bone marrow cultures under conditions which stimulate basophilopoiesis. A high degree of correlation was observed between histamine values and basophil counts in suspension cultures. Cultures of normal marrow with splenic conditioned medium (CM) prepared from spleen cells of ovalbumin (OA)-treated animals or coculture of marrow cells from these animals with autologous spleen cells demonstrated rises in histamine values which paralleled basophil counts, with a mean calculated histamine of 0.3 pg/basophil. Addition to marrow cells from OA-treated animals of autologous splenic T-lymphocytes or culture of normal marrow in the presence of CM derived from PHA-stimulated splenic T-lymphocytes caused in vitro increases in histamine significantly greater than when T-lymphocyte depleted spleen cells or CM derived from the latter were used, respectively (P less than 0.02). The presence of OA in marrow-spleen cultures significantly enhanced basophilopoiesis when whole or T-enriched, but not T-depleted, spleen fractions were used (P less than 0.02). The magnitude of in vitro increases in histamine over one week was 10-30 nanograms, accompanied by appropriate increases in basophils in CM-stimulated normal marrow cultures. From these data it can be concluded that histamine is an independent criterion of basophilopoiesis in vitro. An entirely new population of histamine-synthesizing cells appears to arise over 1 week in vitro under conditions of antigen or T-cell product stimulation.