Gamma interferon enhances mitogenic responses induced by pokeweed mitogen

Immunomodulatory activity of beta-casein permeate medium fermented by lactic acid bacteria

During fermentation, lactic acid bacteria may be able to release components that possess immunomodulatory activity. This activity was investigated in several culture supernatants arising from lactic acid bacteria cultured in a medium composed primarily of UF permeate of bovine milk; beta-CN was added as the sole protein source. Only a Lactobacillus helveticus supernatant allowed the modulation (both suppression and enhancement) of lymphocyte proliferation in vitro on human peripheral blood lymphocytes, but L. helveticus did not modulate the cytotoxic activity of natural killer cells or of lymphokine-activated killer cells. The addition of different quantities of culture supernatant to cultures of human mononuclear cells, stimulated by the mitogen concanavalin A, significantly increased the production of interferon-gamma and decreased the production of interleukin-2 and the expression of the alpha-chain of the interleukin-2 receptor (p55), all of which appear to be correlated with the decrease in lymphocyte proliferation. Our results suggest that the culture supernatant activity might be related to interaction with monocyte-macrophage and T helper cells, especially Th1-like cells.

Mitogenic activity of selenoorganic compounds in human peripheral blood leukocytes

A variety of organoselenium compounds were originally described as antiinflammatory, antioxidant or glutathione-peroxidase-like agents, and as inhibitors of prostaglandin and leukotriene synthesis. Recently, the compounds have also been found to be inducers of interferon gamma and tumor necrosis factor in human peripheral blood leukocytes (PBL). We evaluated the effects of bis [2-(N-phenylcarboxamido)phenyl] diselenide and Ebselen; 2-phenyl-1,2-benzisoselenazol-3(2H)one, on the incorporation of tritiated thymidine into the DNA of PBL cultured in vitro. Both compounds were mitogenic and this effect was correlated with the expression of interleukin 2 receptor in T-lymphocytes. Therefore, we suggest that the selenoorganic compounds may induce mitogenic cytokines.

Dipeptidyl peptidase IV in human T lymphocytes. Impaired induction of interleukin 2 and gamma interferon due to specific inhibition of dipeptidyl peptidase IV

Specific inhibitors of the membrane-bound dipeptidyl peptidase IV (DP IV) and polyclonal antibodies against this enzyme were used to investigate the relationships between DP IV activity and the production and action of T cell-derived lymphokines. Production of interleukin 2 (IL-2) and gamma interferon by mitogen plus phorbol ester-stimulated mononuclear cells from human blood was found to be reduced in the presence of N-Ala-Pro-O-(nitrobenzoyl-)-hydroxylamine, epsilon-(4'-nitro) benzoxycarbonyl-Lys-Pro, and anti-(DP IV) immunoglobulin in a dose-dependent manner. Moreover, the proliferative response of mitogen-stimulated mononuclear cells to IL-2 is impaired in the presence of DP IV inhibitors. Therefore it is suggested that the membrane peptidase DP IV is involved in the induction and activation of cytokines controlling lymphocyte proliferation.

Interferon-alpha and interferon-gamma as regulators of human adult and newborn B-cell function

The role of interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma) in the regulation of B-cell function was studied using highly purified tonsillar B-cells and unfractionated mononuclear cells from healthy adults and newborns. Recombinant IFN-gamma (rIFN-gamma) was found to enhance Staphylococcus aureus Cowan I (SAC)-induced proliferation of purified B-cells. Recombinant IFN-alpha (rIFN-alpha) neither enhanced nor inhibited the function of purified B-cells. However, when unfractionated mononuclear cells were studied, no enhancement in SAC- or pokeweed mitogen (PWM)-induced proliferation was found in response to these IFNs. In fact, the responses in these cultures were mainly inhibitory. The effects were dependent on the mitogen used for activation of the cells and on the source of the cells. The IFNs acted in a more inhibitory way in cultures stimulated with PWM than in those stimulated with SAC. In addition, they acted more suppressively in cord blood mononuclear cells (CBMCs) than in adult peripheral blood mononuclear cells. PWM was found to decrease CD4+/CD8+ T-cell ratio, and cells with suppressor function physiologically dominate among CBMCs. Thus, the effect of these interferons on B-cell function seems to depend on the magnitude of suppressor cell function among the cell population.