Interleukin-12 and tumor necrosis factor alpha mediate innate production of gamma interferon by group B Streptococcus-treated splenocytes of severe combined immunodeficiency mice

Abstract

The existence of interleukin-12-mediated innate immune responses to group B streptococci (GBS) was tested by examining T-lymphocyte-independent gamma interferon (IFN) production in cultured splenocytes from severe combined immunodeficiency mice. Splenocytes were cultured with killed or living GBS for 48 h, and then IFN was measured by enzyme-linked immunosorbent assay. Type III GBS as well as other extracellular bacterial agents of neonatal sepsis (staphylococci and enterococci) induced IFN production, which was enhanced by interleukin-2 and was inhibited by neutralizing antibodies to tumor necrosis factor alpha and to mouse interleukin-12. Interleukin-12 bioactivity was present in conditioned medium from GBS-treated adherent macrophages. Adherent peritoneal macrophages and bone marrow-derived natural killer cells from severe combined immunodeficiency mice cultured separately with GBS did not produce IFN, whereas cocultures did produce IFN. Functional macrophage activation was evident by nitric oxide production in GBS-treated splenocyte cultures. The results show that extracellular pathogens such as GBS, similarly to intracellular microbes, induce macrophage interleukin-12 and tumor necrosis factor alpha, which promote natural killer cell secretion of IFN, which then enhances innate phagocyte resistance mechanisms.

Effect ofAlloiococcus otitidisand three pathogens of otitis media in production of interleukin-12 by human monocyte cell line

“…The exposure of macrophages to group B Streptococcus and other extracellular bacterial agents of Staphylococci and Enterococci result in the production of bioactive IL‐12 [13]. In our study, a reduction of IL‐12 production was seen by pre‐treatment of the bacteria with GA or by heat.…”

Cytokine Response to Group B Streptococcus Infection in Mice

“…Lane designations are identical for blots and histograms. [51]. These investigators also suggested that IFN-g could have a role in non-specific resistance to GBS, inducing feedback activation of macrophages.…”

“…For example, a previous report examining the role of complement in determining the phagocytosis of GBS-III by peritoneal murine macrophages in the absence of immune serum, has underlined that C3-dependent binding may be important for mononuclear phagocyte-dependent clearance of GBS from the blood of patients with a deficiency of type-specific antibodies [60]. Other authors, on the basis of results obtained in an animal model of in vitro GBS-III infection, have suggested that activation of NK cells with IFN-g release could be a critical event, during in vivo infection, in promoting bactericidal functions of neutrophils and macrophages [51,61,62]. Contrary to these speculations, in our experimental model, the increase of important functions of the natural immune system, such as splenic NK activity and microbicidal activity of splenic mononuclear and polymorphonuclear phagocytes induced in vivo by GBS-Ia, did not seem to have any effect on resistance to infection, which in fact rapidly became lethal.…”

“…Candida albicans yeast cells were labelled with 300 mCi of Na 2 51 CrO 4 for 2 h at 37ЊC. The 51 Cr release assay and the calculation of the percentage of specific release were performed as described previously [34].…”

“…Calculation of lytic units. Dose-response curves were obtained in selected experiments by plotting the percentage of specific 51 Cr release and the effector-to-target ratio (three to five for each curve). The best-fit curve for these functions was logarithmic (Hewlett-Packard calculator H-p 97: program standard Pac.…”