HISTAMINE-RELEASING ACTIVITY AND ITS INHIBITION BY SUPERNATANTS FROM CULTURED LYMPHOID-CELLS OF NIPPOSTRONGYLUS-BRASILIENSIS-INFECTED RATS

The influence of Nippostrongylus bransiliensis infection on the capabi lity of HRF (Histamine Releasing Factor) generation by rat lymphoid ce lls in vitro has been studied. Spleen cells and thymocytes of normal a nd Nippostrongylus brasiliensis-infected rats were cultured in the pre sence of nonspecific mitogen (PHA) or specific N. brasiliensis antigen (NbAg), and cell-free supernatants fractionated by Sephadex G-75 chro matography were tested on homologous mast cells for histamine releasin g activity. The results show that PHA-stimulated lymphoid cells from b oth normal and infected rats produced a factor releasing histamine fro m mast cells. Histamine releasing activity was not detected when lymph oid cells of N. brasiliensis-infected rats were cultured in the presen ce of NbAg. Moreover, supernatants of these cultures diminished HRF-in duced histamine release from mast cells, suggesting the production of factor(s) inhibiting this release. This histamine release inhibiting a ctivity was detected in fractions in Sephadex G-75 chromatography of s upernatants from the cultures of NbAg-stimulated thymocytes of infecte d rats.