Lymphokine factors inducing IgG production in human B-cell line ARH-77 and stimulatory effects of phorbol ester tumor promoter

Independent regulation of B-cell inducing factor and IL-2 production by T lymphocytes, and direct and indirect promotion of immunoglobulin secretion by glucocorticosteroid

The conditions for induction of B-cell inducing factor (BIF) by human peripheral blood T cells was investigated. BIF was assayed by induction of immunoglobulin secreting cells (ISC) in peripheral blood B (non-T) cells stimulated with Staphylococcus aureus bacteria strain Cowan I (Sac), and in the IgM cell line SKW6.4. Maximum BIF production occurred with high concentrations of the T-cell mitogens phytohemagglutinin, concanavalin A, and PWM. Dexamethasone (Dex) also induced BIF production in T cells at 10(-5) to 10(-7) M. At 10(-5) and 10(-6) M Dex, the T-cell supernatants had to be dialyzed before testing because Dex alone stimulated variable levels of ISC in both test B-cell assays. Dex did not enhance BIF production by T cells that were optimally stimulated by lectin. BIF levels were maximum by Day 2 of T-cell cultures and remained high at Days 3 and 4. In contrast, IL-2 reached a peak at Day 1 and declined drastically by Day 4. We previously showed that IL-2 at less than 100 U/ml did not induce ISC in B cells and did not alter ISC induction by BIF. Dex did not induce IL-2 production and inhibited IL-2 production induced by Con A, in contrast to the promoting effects of Dex on BIF production, providing further evidence for the independence of BIF and IL-2 production and B-cell stimulation.

Effect of carrageenan on the histology of the bursa of fabricius and the humoral immune response to Salmonella O antigen

Bursal secretory cells have been studied with light and electron microscope after prolonged carrageenan treatment. Intravenous injected carrageenan decreased the number of secretory cells as early as 4 days after the first carrageenan administration. Degranulation of the secretory cells may have made it difficult to identify these cells. The discharge of granules from the secretory cells was indicated by the appearance of a large amount of extracellular substance on the cell surface. The carrageenan may have accelerated the IgM-IgG switch after immunization with Salmonella O antigen. The rapid IgM-IgG switch was preceded by degranulations of the secretory cells. Therefore, the secretory products of the cells might have contributed to the switch. The number of secretory cells in the carrageenan-treated birds increased by the secondary immunization. Many of these secretory cells were immature and located close to the corticomedullary border. The young cells revealed a large blastlike nucleus and bulky cytoplasm with granules surrounding the cytocentrum and Golgi zone.