Biomedical subjects

M C Ruzek

Publications and source records attributed to M C Ruzek.

8 recordsLinked to original sources

PubMed1997

Characterization of early cytokine responses and an interleukin (IL)-6-dependent pathway of endogenous glucocorticoid induction during murine cytomegalovirus infection.

Early infection with murine cytomegalovirus (MCMV) induces circulating levels of interleukin (IL)-12, interferon (IFN)-gamma, and tumor necrosis factor (TNF). Studies presented here further characterize these responses by defining kinetics and extending evaluation to include IL-1, IL-6, and glucocorticoids. IL-12 p40, IFN-gamma, TNF, IL-1alpha, and IL-6 were shown to be increased, but IL-1beta was undetectable, in serum of MCMV-infected mice. The IL-12 p40, IFN-gamma, TNF, and IL-6 responses were dramatic with peak levels reaching >150-10,000 pg/ml at 32-40 h after infection and rapidly declining thereafter. Glucocorticoid induction, peaking at 36 h and reaching 30-fold increases above control values, accompanied the cytokine responses. Mice with cytokine deficiencies or neutralized cytokine function demonstrated that IL-6 was the pivotal mediator of the glucocorticoid response, with IL-1 contributing to IL-6 production. The IL-6 requirement appeared to be specific for virus-type stimuli as the synthetic analogue of viral nucleic acid, polyinosinic-polycytidylic acid, also induced IL-6-dependent glucocorticoid release, but treatments with the bacterial product lipopolysaccharide and a non-immune physical restraint stressor elicited IL-6-independent responses. Collectively, the results identify IL-6 as a primary mediator of glucocorticoid induction, and elucidate specific pathways of interactions between immune and neuroendocrine systems during viral infection.

Adrenocorticotropic Hormone↗

PubMed1997

Plasma IgE levels, activation marker expression, and cytokine production in non-atopic individuals.

BACKGROUND: Since human IgE serum levels are very low compared with the other immunoglobulin isotypes, most studies have examined the regulation of IgE production in severely atopic individuals where serum IgE levels are increased. Since atopy is a pathologic consequence of increased IgE production, this disease state could have other influences that result in abnormal expression of these parameters and may not reflect normal IgE regulatory mechanisms. OBJECTIVE: To study nonatopic individuals to examine the expression of IgE regulatory cytokines as well as additional cell surface activation markers in relation to serum IgE levels. METHOD: We selected ten individuals at both the lower and higher end of a spectrum of plasma IgE concentrations from 29 nonatopic individuals and compared the differences in cytokine and activation marker expression in relation to IgE production. RESULTS: We found that even upon extensive examination of activation markers on T, B, and NK cell subsets, there are no significant differences in the cell populations or surface marker expression between the high IgE and low IgE groups. Messenger RNA expression in peripheral blood mononuclear cells (PBMCs) of the cytokines IL-4 and IL-6 was significantly higher, whereas IL-10 was lower in the high IgE group. In addition upon in vitro polyclonal stimulation of peripheral blood mononuclear cells, individuals of the high IgE group produced lower levels of IL-2, IFN gamma and IL-10 compared to the low IgE donors. CONCLUSION: Since our results differ from studies using atopic individuals, this study demonstrates the importance of using nonatopic individuals for examining associations between various immune parameters and IgE.

Antigens, CD↗

PubMed1996

A combination of IL-10 and direct contact with plasma cell tumors decreases CD23 expression on splenic B cells.

We and others have previously found that splenic B cells from plasma cell tumor-bearing mice exhibit decreased CD23 expression. In the present study we further examined the mechanism of CD23 down-regulation by plasma cell tumors. We show here that although direct contact is required between the tumor cells and B cells, it is not sufficient, since fixed tumor cells do not induce the same reduction in CD23 expression. We have identified IL-10, a cytokine produce by the tumors, as the sole soluble factor that contributes to decreased CD23 expression on B cells induced by plasma cell tumors because 1) Abs to IL-10 prevent the loss of CD23 induced by plasma cell tumors both in vitro and in vivo; 2) engineered IL-10 negative variants of these tumors are reduced in their ability to down-regulate CD23 expression; 3) rIL-10 alone induces partial, but significant, decreases in CD23 expression on normal splenic B cells; and 4) the addition of IL-10 and fixed tumor cells to cultures of normal splenocytes decreases CD23 expression to levels similar to those in cocultures with live tumor cells. Collectively, these results demonstrate that plasma cell tumors down-regulate CD23 expression on B cells by a coordinate mechanism of IL-10 plus contact-mediated events and reveal a novel role for IL-10 in the regulation of CD23 expression on B cells that is suggestive of host B cell activation in the presence of the tumor.

Animals↗

PubMed1996

Decreased production of IL-2 and IFN-gamma by stimulated splenocytes from mice bearing plasma cell tumors is associated with alteration of DNA-binding factors.

We have previously demonstrated that polyclonally stimulated splenocytes as well as enriched T cells from mice bearing plasma cell tumors (PCT) show decreased production of the Th1-associated cytokines, IL-2 and IFN-gamma. This observed loss of IL-2 and IFN-gamma production could be attributed to possible alterations in various factors required for T cell activation and cytokine production. We find that B7 co-stimulatory molecules and IL-2R are up-regulated normally on splenocytes from PCT mice. Concanavalin A (Con A) stimulation of splenocytes from PCT mice in the presence of immobilized anti-CD28 antibody does not enhance proliferation. Exogenous rIL-2 addition to cultures of splenocytes from PCT mice also does not enhance proliferative responses or cytokine production. Furthermore, we do not observe inhibition of normal splenocyte proliferation and IL-2 production in the presence of splenocytes from PCT mice, suggesting that the appearance of suppressor cells cannot account for the decreased responses by splenocytes from PCT mice. Also, IL-2 mRNA levels are decreased in stimulated splenocytes from PCT mice, suggesting that there may be an alteration of transcription factors required for activation of IL-2. Therefore, we have evaluated the DNA-binding activity of transcription factors involved in activation of IL-2 and IFN-gamma gene transcription. We find that binding activities of AP-1, Oct-1 and Oct-2 transcription factors in stimulated splenocytes from PCT mice are similar to normal splenocytes. However, the binding activities of NF-kappa B complexes and factors that bind to the proximal conserved element in the IFN-gamma promoter are dramatically altered in splenocytes from PCT mice. These results suggest that PCT induce changes in certain transcription factors that are important for anti-tumor responses, including T cell proliferative responses and Th1-associated cytokine production.

Animals↗

PubMed1996

In vitro and in vivo recovery of IFN-gamma, but not IL-2, production by IL-12 in mice with plasma cell tumors.

We have previously found that T cells from mice bearing plasma cell tumors (PCT mice) demonstrate decreased proliferation as well as decreased production of the Th 1-associated cytokines IL-2 and IFN-gamma in response to polyclonal stimulation. In the present study, we have examined soluble factors as possible elements required to rescue this decreased proliferation and cytokine production by splenocytes from PCT mice. We find that the addition of supernatants from stimulated normal splenocytes has no effect on proliferation of IL-2 production by splenocytes from PCT mice. In contrast, these supernatants completely restore IFN-gamma production by splenocytes from PCT mice. We have found that IL-12 is responsible for the observed increase in IFN-gamma production because: (i) addition of anti-IL-12 antibody blocks this recovery of IFN-gamma production by these supernatants, (ii) the addition of recombinant IL-12 to cultures of splenocytes from PCT mice results in increased IFN-gamma production and (iii) in vivo treatment of PCT mice in IL-12 also results in increased IFN-gamma production by the subsequently activated splenocytes, but has little effect on proliferation or IL-2 production. These results demonstrate that both in vitro and in vivo, IL-12 selectively restores the decreased production of IFN-gamma by splenocytes from PCT mice.

Animals↗

PubMed1995

Plasma cells tumors decrease CD23 mRNA expression in vivo in murine splenic B cells.

CD23, the low-affinity Fc receptor for IgE, is constitutively expressed on mature, naive B cells, but is lost following B cell activation. We and others have shown that CD23 expression on B cells decreases in mice bearing plasma cell tumors. In contrast to these findings, we find that IgE-secreting tumors do not cause a loss of CD23 expression on host splenic B cells. Decreased expression of CD23 on B cells induced by plasma cell tumors requires direct contact between tumor cells and B cells; and other host cells are not involved. The loss of surface CD23 expression is associated with a decrease in steady-state CD23 mRNA levels in B cells from plasma cell tumor-bearing mice. Interestingly, loss of CD23 mRNA is observed even in B cells from mice with IgE-secreting tumors, where we find surface CD23 protein expression to be similar to that of normal mice. The maintenance of surface CD23 expression on B cells in mice with IgE-secreting tumors is dependent solely on the presence of IgE, and is not a tumor-specific effect. Therefore, we conclude that in vivo, IgE secreted by plasma cell tumors can result in the maintenance of normal levels of surface CD23 expression by a post-transcriptional mechanism, even when the tumor induces a down-regulation of CD23 mRNA levels.

Animals↗

PubMed1995

Specific decrease of Th1-like activity in mice with plasma cell tumors.

Previously we examined the ability of the host's immune responses to regulate Ig production in an IgE-secreting murine plasma cell tumor (B53). In the present study we have examined the reverse phenomenon, in that we have investigated the effects of this and other plasma cell tumors on the immune responses of their hosts. We found that splenocytes from plasma cell tumor-bearing mice demonstrate decreased proliferation in response to polyclonal stimulation by either Con A or a combination of PMA and calcium ionophore (A23187). Fractionation of the splenocytes demonstrated that this reduction in proliferation was confined to CD4+ T cells and that the proliferation of CD8+ T cells was unaffected. In order to determine whether the down-modulatory effects of the tumor were confined to a particular CD4+ helper T cell subset, we examined the production of cytokines representing the Th1 subset (IL-2 and IFN-gamma) and the Th2 subset (IL-4 and IL-10) from stimulated splenocytes and from stimulated enriched splenic T cells. We found that both stimulated splenocytes and T cells from plasma cell tumor-bearing mice produced lower levels of the Th1 cytokines IL-2 and IFN-gamma compared with normal cultures, demonstrating that Th1-like responses are inhibited in the hosts of these tumors. However, no alterations in the production of the Th2 cytokines IL-4 and IL-10 were observed in these stimulated splenocyte or T cell cultures from the tumor-bearing mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Metabolism of 2-aminofluorene by human polymorphonuclear leukocytes: more evidence for the association between inflammation and cancer.

Recent investigations have demonstrated the ability of leukocytes to metabolize promutagens or procarcinogens into their genotoxic forms. As a possible explanation for the association between inflammation and cancer, we and others have hypothesized that local accumulations of leukocytes could take up nearby promutagens, metabolize them, and release genotoxic agents that may cause damage in the surrounding tissue. Using a modified, two-step preincubation protocol with Salmonella, we have tested this hypothesis. We have shown that total human peripheral blood leukocytes, cultured in the presence of 2-aminofluorene for 18 hr, can metabolize 2-aminofluorene into agents mutagenic to Salmonella typhimurium strain TA98. Furthermore, experiments in which polymorphonuclear leukocytes were separated from mononuclear leukocytes demonstrated that the PMNs metabolized 2-aminofluorene to a much greater extent than the MNs.

Fluorenes↗