Rat IgG1 kappa Isotype Control [APC]

To investigate the influence of oxidative stress on the immune response, mice were injected with H2O2, and peritoneal macrophages were isolated and stimulated in vitro with lipopolysaccharide (LPS). H2O2 significantly augmented both interleukin (IL)-12p40 and IL-12p70 production and increased the p40/p70 molecular ratio. This was confirmed by mRNA analysis, which showed that H2O2 increased LPS-induced mRNA expression of both IL-12p40 and IL-12p35 subunits with an increased p40/p35 ratio. Analysis of anti-ovalbumin (OVA) antibodies revealed that H2O2 injection significantly increased the production of type 2 helper T cell (Th2)-associated antibody classes [immunoglobulin (Ig)E and IgG1] but not a Th1-associated antibody class (IgG2a). To confirm the Th2-predominant immune response, we analyzed the profile of cytokine production by spleen T cells of OVA-immunized and H2O2-injected mice. H2O2 significantly increased the production of IL-4 but not that of interferon-gamma. Together, these results suggest that H2O2-induced overproduction of IL-12p40 promotes the Th2-predominant response through increased production of IL-12p40-homodimers, which could serve as an antagonist of the Th1-inducing cytokine IL-12p70.

Using model tumor T cell lines, protein kinase C (PKC) a has been implicated in IL-2 cytokine promoter activation in response to Ag receptor stimulation. In this study, for the first time, PKC alpha null mutant mice are analyzed and display normal T and B lymphocyte development. Peripheral CD3(+) PKCa-deficient T cells show unimpaired activation-induced IL-2 cytokine secretion, surface expression of CD25, CD44, and CD69, as well as transactivation of the critical transcription factors NF-AT, NF-kappa B, AP-1, and STAT5 in vitro. Nevertheless, CD3/CD28 Ab- and MHC alloantigen-induced T cell proliferation and IFN-gamma production are severely impaired in PKC alpha(-/-) CD3(+) T cells. Consistently, PKCa-deficient CD3(+) T cells from OVA-immunized PKCa-deficient mice exhibit markedly reduced recall proliferation to OVA in in vitro cultures. In vivo, PKCa-deficient mice give diminished OVA-specific IgG2a and IgG2b responses following OVA immunization experiments. In contrast, OVA-specific IgM and IgG1 responses and splenic PKC alpha(-/-) B cell proliferation are unimpaired. Our genetic data, thus, define PKCa as the physiological and nonredundant PKC isotype in signaling pathways that are necessary for T cell-dependent IFN-gamma production and IgG2a/2b Ab responses.