Antigen presenting cells (APCs) from thermally injured and/or septic rats modulate CD4+ T cell responses of naive rat

Abstract

Regulation of immune response is marked by complex interactions among the cells that recognize and present antigens. Antigen presenting cells (APCs), the antigen presenting cell component of the innate immune response plays an important role in effector CD4+ T cell response. Thermal injury and/or superimposed sepsis in rats' leads to suppressed CD4+ T cell functions. We investigated modulations of CD4+ T cell function by APCs (purified non-T cells) from thermally injured and/or septic rats. Rats were subjected to 30% total body surface area scald burn or exposed to 37 degrees C water (Sham burn) and sepsis was induced by cecal-ligation and puncture (CLP) method. At day 3 post-injury animals were sacrificed and CD4+ T cells and APCs from mesenteric lymph nodes (MLN) were obtained using magnetic microbead isolation procedure. APCs from injured rats were co-cultured with sham rat MLN CD4+ T cells and proliferative responses (thymidine incorporation), phenotypic changes (Flow cytometry), IL-2 production (ELISA) and CTLA-4 mRNA (RT-PCR) were determined in naive rat CD4+ T cells. The data indicate that APCs from thermally injured and/or septic rats when co-cultured with CD4+ T cells suppressed CD4+ T cell effector functions. This lack of CD4+ T cell activation was accompanied with altered co-stimulatory molecules, i.e., CD28 and/or CTLA-4 (CD152). In conclusion, our studies indicated that defective APCs from thermally injured and/or septic rats modulate CD4+ T cell functions via changes in co-stimulatory molecules expressed on naive CD4+ T cells. This altered APC: CD4+ T cell interaction leads to suppressed CD4+ T cell activation of healthy animals.

Contribution of programmed cell death receptor (PD)-1 to Kupffer cell dysfunction in murine polymicrobial sepsis

“…Furthermore, these findings of altered mediator release are underpinned by observations that septic mouse macrophages appear to be differentially utilizing/ activating various signaling pathways (21,23,24,41,52,53) and the upregulation/expression of inhibitory receptors like programmed cell death receptor-1 (PD-1), CD40, etc. (22,25,30,54). Also, while the loss of immune cells via apoptosis is evident in these animals (28,46,59), this is likely, at least in part, a response to the actions of immunesuppressive cell populations or the anti-inflammatory mediators they release (3,40,58).…”

Thermal injury-plus-sepsis contributes to a substantial deletion of intestinal mesenteric lymph node CD4+ T cell via apoptosis

“…Our present studies have assessed both the individual effects of TI and sepsis as well as an effect of superimposition of sepsis on TI, in rats, on apoptotic responses of MLN CD4 + T cells. While TI or sepsis individually produced low animal mortality, the combined injury resulted in exacerbation of both morbidity and mortality 17,19. Thus, the focus in this study on the combined TI-plus-sepsis injury affords us an opportunity to assess potential non-lethal versus lethal implications of the T cell dysfunction.…”

“…A number of laboratory and clinical studies have shown that extensive thermal injury induces a state of immune-insufficiency, and that the immune-refractoriness predisposes the injured host to critical morbidity and mortality 7 , 9 , 12 - 16 . To date, their involvement as critical regulatory molecules responsible for T cell suppression in TI and septic injuries continues to be a subject of extensive studies as evident from reports from several laboratories 17 - 20 . The principal outcome of such immune suppression is increased susceptibility of injured host to opportunistic pathogens causing high risk of death.…”

Melatonin Plays a Protective Role in Postburn Rodent Gut Pathophysiology

“…All animal housing, experimentation and treatment were based on previously published protocols approved by the Chicago State University Animal Care and Use Committee (IACUC) and in accordance with NIH guidelines 1-3. All rats (1) were acclimatized in the animal facility for at least one week before being subjected to any treatment; (2) were given free access to water and standard lab rat chow ad libitum and kept in a 12:12 light-dark from time of arrival till sacrifice; and (3) unless otherwise noted, all treatments including major thermal injury (TI) were carried out between zeitgeber time (ZT) 6 and 8, where ZT 0 represents the onset of the light period of the L-D cycle at 6 a.m. Major thermal injury protocols were previously described and shown to be associated with full thickness 3rd degree skin burns over ~30% of the total body surface associated with fairly consistent inflammation-linked immune as well as gut barrier abnormalities 1-3. Accordingly, upon verification of deep anesthesia with sodium pentobarbital (40-50 mg/kg intraperitoneal, i.p.…”

“…These observations point to a great therapeutic potential, especially in relation to gut barrier inflammatory abnormalities associated with major thermal injury and postburn intestinal sepsis pathogenesis 1-3. Here, we begin to closely explore this potential by examining melatonin's postburn gut pathophysiological dynamics.…”