Cellular immunity in burns

Effects of Pentoxyfylline on Mesenteric Lymph Node T-Cells in a Rat Model of Thermal Injury

Cutaneous burn injury-induced T lymphocyte suppression is a well-known phenomenon. In this study, we evaluated the effect of treatment of burn rats with pentoxifylline (PTX) on the burn-induced suppression of T lymphocytes. Anesthetized rats were subjected to 30% total body surface area burn by exposing skin to 95 degrees C water for 10 s. T lymphocytes were isolated from sham and burn rats with or without PTX treatment (120 mg/kg, ip). T cell proliferation and interleukin (IL)-2 production in response to T cell mitogen concanavalin A was measured using 3 H-thymidine uptake and enzyme-linked immunosorbent assay, respectively. P59 fyn autophosphorylation and its kinase activity was determined using in vitro kinase assay. In addition, T lymphocyte Ca2+ signaling was assessed using Ca2+ imaging technique. Two days after injury, there was a significant decrease in mesenteric lymph node T cell proliferation and IL-2 production in burn injured rats compared with those obtained from sham-injured rats. This decrease in T cell proliferation and IL-2 production in burn-injured rats was accompanied by a significant suppression in both P59 autophophorylation and kinase activity as well as Ca2+ signaling. Treatment of burn-injured rats with PTX produced a near complete recovery of T cell proliferation and IL-2 production. Furthermore, PTX treatment also prevented the burn-mediated suppression in P59fyn and kinase activity as well as restored Ca2+ signaling similar to those observed in sham injured rats. These findings altogether suggested that PTX treatment attenuate T cell suppression in burn-injured rats and that the effects of PTX are mediated via modulating P59 fyn and Ca2+ signaling.

Effects of burn with and without Escherichia coli infection in rats on intestinal vs. splenic T-cell responses

OBJECTIVE

To evaluate the effect of burn injury with and without an Escherichia coliseptic complication on T-cell proliferation, interleukin-2 production, and Ca(2+) signaling responses in intestinal Peyer's patch and splenic T cells.

DESIGN

Prospective, randomized, sham-controlled animal study.

SETTING

University medical center research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Rats were subjected to a 30% total body surface area, full skin thickness burn. Infection in rats was induced via intraperitoneal inoculation of E. coli, 10(9) colony forming units/kg, with or without a prior burn.

MEASUREMENTS AND MAIN RESULTS

Rat Peyer's patch and splenic T lymphocytes were isolated by using a nylon wool cell purification protocol. T-cell proliferation, interleukin-2 production, and Ca(2+) signaling responses were measured after stimulation of cells with the mitogen, concanavalin A. T-cell proliferation was determined by measuring incorporation of (3)H-thymidine into T-cell cultures. Interleukin-2 production by T-cell cultures was measured by using enzyme-linked immunosorbent assay. Intracellular T-cell Ca2(+ )concentration, [Ca(2+)](i), was measured by the use of Ca(2+)-specific fluorescent label, fura-2, and its fluorometric quantification. [Ca(2+)](i) was also evaluated by the use of digital video imaging of fura-2 loaded individual T cells. T-cell proliferation and interleukin-2 production were suppressed substantially in both Peyer's patch and splenic T cells 3 days after either the initial burn alone or burn followed by the E. coli inoculation at 24 hrs after the initial burn. There seemed to be no demonstrable additive effects of E. coli infection on the effects produced by burn injury alone. The T-cell proliferation and interleukin-2 production suppressions with burn or burn-plus-infection insults were correlated with attenuated Ca(2+) signaling. E. coli infection alone suppressed T-cell proliferation in Peyer's patch but not in splenic T cells at 2 days postbacterial inoculation; E. coli infection had no effect on Peyer's patch or splenic T cells at 1 day postinjury. On the other hand, burn injury alone caused a substantial T-cell proliferative suppression at 2 days postburn in both Peyer's patch and splenic cells and a significant suppression in T-cell proliferation on day 1 postburn in Peyer's patch but not in the spleen.

CONCLUSION

An initial burn injury suppressed T-cell proliferation at a level that it would not be further affected by a subsequent infection even if the infection by itself has the potential of suppressing T-cell proliferation. An earlier onset of T-cell suppression in Peyer's patch cells than in the spleen with burn could be attributable to an initial hypoperfusion-related intestinal mucosal tissue injury. Overall, our study supports the concept that burn injury per se can significantly suppress T-cell mediated immunity and that the intestine is an early tissue site of such suppression.

Monocyte suppressor function in burns: T cell-monocyte interaction in mediating suppression

Reduced in vitro T cell mitogen-induced transformation, low proportion of T cells and increased proportion of non-T cells were found in blood mononuclear cells of patients with severe burns 3-12 days after the injury. High spontaneous proliferation of non-T cells was observed and could be related mainly to the B cell fraction. Monocytes mediated suppression of mitogen-stimulated T cell proliferation. We further studied the role of monocytes in the enhanced suppressor activity of Con A-activated T cells and found that in this assay system, the patient's T cells mediated suppression in collaboration with monocytes. In vitro, increased suppressor function was probably the result of in vivo stimulation of inhibitory activity ascribed to both monocytes and T cells of patients. Addition of indomethacin to cell cultures markedly reduced suppression of lymphocyte proliferation. Less significant reduction was noted when the patient's T cells were activated in vitro by Con A. Adjuvant treatment of burn patients with indomethacin may play a role in alleviating suppression of immune response in these patients.