Induction of global anergy rather than inhibitory Th2 lymphokines mediates posttrauma T cell immunodepression.

Depressed mitogen-induced IL-2 and IFN-gamma responses after severe mechanical or thermal injury are postulated to result from an expansion of Th2 lymphocytes with concomitant excessive production of IL-4 and/or IL-10. Here, we simultaneously assessed proliferation and Th1 (IFN-gamma) versus Th2 (IL-10, IL-4) lymphokine production in trauma patients' isolated T cells stimulated in a costimulation sufficient, antigen presenting cell independent system (anti CD3 + anti-CD4). T cells with depressed proliferation and IL-2 production simultaneously lost IL-4, IL-10, and IFN-gamma protein and mRNA responses. Exogenous IL-12 addition did not restore IFNgamma responses, but exogenous IL-2 partially restored IL-4, IFN-gamma, and IL-10 production. Although initially partially restored by exogenous IL-2 or stimulation with PMA + ionomycin, patient T cells with persisting anergy progressively lost even these lymphokine and proliferative responses. Development of global T cell anergy was not a result of lost T cell viability or protein synthesis, since it corresponded to predominance of anergic T cells with upregulated expression of CD11b, but downregulated CD28 and CD3 expression. Thus, the subset of posttrauma patients whose isolated T cells become unresponsive experienced progressively worsening global anergy, mediated not by an increased production of Th2 lymphokines, but possibly by T cell incapacity to be activated through TCR triggering or Ca(2+) mobilization.

Increased monocyte TNF-alpha message stability contributes to trauma patients' increased TNF production.

Post-trauma elevation of tumor necrosis factor alpha (TNF-alpha) appears to be critical in mediating many symptoms of systemic inflammatory response syndrome (SIRS), resulting in late mortality. Although increased monocyte (mphi) TNF-alpha production plays a pivotal role in this TNF-alpha elevation, the molecular mechanisms leading to increased mphi TNF-alpha production have yet to be elucidated. We demonstrate that, although TNF-alpha mRNA levels are increased in all trauma patients' mphi, which produce elevated levels of TNF-alpha protein, in the majority of patients, these increased TNF-alpha mRNA levels are under normal transcriptional and posttranscriptional control. Consequently, the increased TNF-alpha production by these patients' mphi is probably due to preactivation of these mphi by trauma-released mediators. However, a small minority of patients, whose mortality rate was 57%, produce TNF-alpha of primarily the membrane-associated type. The mphi TNF-alpha mRNA accumulation of these patients in response to in vitro stimulation is significantly augmented. All of these patients experienced SIRS. In this subset of patients' mphi, TNF-alpha mRNA stability was aberrantly increased. Such an increase in TNF-alpha mRNA stability could lead to devastatingly prolonged production of TNF-alpha protein. This demonstration of increased TNF-alpha mRNA stability in post-trauma mphi represents a novel correlation of elevated membrane-associated TNF-alpha protein, increased mortality, and a mechanism for this occurrence.

Only a subset of trauma patients with depressed mitogen responses have true T cell dysfunctions.

Many studies have demonstrated depressed mitogenic responses in trauma/burn patients' peripheral blood mononuclear cells (PBMC). However, data attributing the relative contribution of secreted inhibitory factors versus a true T cell dysfunction to these depressed mitogenic responses have been conflicting. We have characterized the T cell dysfunctions in posttrauma mitogen depression by simultaneously assessing patient T cell proliferation in the phytohemagglutinin-stimulated PBMC and in the purified T cell population induced with anti-CD3 + anti-CD4. Patients' samples showed three distinct patterns or progressive phases of T cell responses: (i) normal or elevated T cell proliferation in both the whole PBMC and the isolated T cell population (phase I); (ii) depressed T cell proliferation in the PBMC but normal, or even elevated, proliferation in the isolated T cell population (phase II); and (iii) depressed T cell proliferation in both the PBMC and the isolated T cell population (phase III). Patients whose T cells exhibited only a phase I response experienced no major complications with a positive clinical outcome. Patients whose T cell alterations progressed to phase II experienced infectious episodes and some complications, but all had positive clinical outcomes. In contrast, patients whose T cells progressed to phase III dysfunction had severe clinical complications (multiple organ failure), with a negative clinical outcome (80% mortality). Patients whose T cells had a phase I or phase II response pattern had no true T cell dysfunctions in the absence of monocytes. However, patients whose T cells had a true T cell dysfunction (phase III) response pattern were at high risk for mortality. Thus, a true T cell dysfunction, though occurring in only a minority of trauma patients, is predictive of clinical outcome.

A membrane TNF-alpha/TNFR ratio correlates to MODS score and mortality.

This study hypothesizes that post-trauma elevated membrane-associated tumor necrosis factor-alpha (mTNF) and decreased TNF receptor shedding may be more related to development of multiple organ dysfunction syndrome (MODS) than elevated secreted TNF-alpha. We also address several of the possible reasons for the previous conflicting reports in studies correlating trauma patients sera TNF-alpha levels to their clinical outcome. These are 1) the lack of an objective quantitative score of clinical illness severity, 2) the lack of multiple TNF-alpha measurements in one patient to allow for trend analysis, 3) the lack of analysis of membrane-associated as well as secreted TNF-alpha levels, 4) the lack of concomitant analysis of soluble TNF-alpha receptors which may bind TNF-alpha in the serum, and 5) the possible requirement for more than one dysfunction in monocyte (M phi) TNF-alpha production and regulation to initiate pathology. Here, the MODS score was used to quantitate patients' illness severity over the length of their intensive care unit (ICU) stay. Patients' and normals' monocytes (stimulated and unstimulated) were assessed for production of secreted as well as membrane-associated TNF-alpha (sTNF and mTNF) and for shed p75 TNF-alpha receptor (TNFR) levels. These parameters of M phi TNF-alpha production and regulation were correlated to the MODS score as an indicator of clinical outcome. There was no correlation between sTNF and MODS score (p = .9025). There was a correlation between increased mTNF (p = .057) or decreased TNFR shedding (p = .0021) to increased MODS, but this lacked specificity. However, when the stimulated M phi production of mTNF and TNFR are expressed as the mTNF/TNFR ratio, an increased ratio correlates with high specificity to development of organ failure (p = .0002). These data indicate that a dual deregulation in M phi TNF-alpha production reflects increasing mTNF-alpha levels concomitant to decreased M phi shedding of neutralizing TNFR and correlates with the development of MODS.

Elevated IL-8 production by trauma patients' monocytes is associated with elevated secretion of TNF alpha.

IL-8 is a recently described chemokine that increases polymorphonuclear neutrophil infiltration and has been implicated in inflammatory pathology. This study assesses monocyte (M phi) interleukin-8 (IL-8) levels in severe trauma patients (injury severity score > 16) who have elevated levels of M phi cell-associated tumor necrosis factor alpha (TNF alpha), a major marker for systemic inflammatory response syndrome after injury. We demonstrate elevated (p = .0007) levels of M phi IL-8 only in those trauma patients who also have increased (p = .0001) M phi-secreted TNF alpha whereas the patients having normal M phi-secreted TNF alpha levels have normal or even decreased M phi IL-8 production. There is no association between M phi IL-8 production and cell-associated TNF alpha levels. M phi induction by Fc gamma RI cross-linking, a common induction pathway in trauma patients' M phi that increases the production of both cell-associated and secreted TNF alpha, can also increase (p = .0022) M phi IL-8 levels. Therefore, post-trauma elevation of M phi IL-8 levels may be associated with increased secreted TNF alpha resulting from, at least in part, Fc gamma RI cross-linking stimulation in vivo.

Altered IL-10 levels in trauma patients' M phi and T lymphocytes.

Trauma results in concomitant immunosuppression and elevated monocyte (M phi) inflammatory cytokine levels. The augmenting or ameliorating effect of IL-10 in septic complications after trauma is controversial. Here, IL-10 levels of trauma patients' and normals' PBMC, isolated M phi, and isolated T cells were assessed and correlated to their PBMC mitogen responses, their T-cell proliferation in an APC independent system, and their M phi production of elevated TNF-alpha levels. Trauma patients with depressed PBMC responses to PHA stimulation also had significantly decreased IL-10 levels in their stimulated PBMC supernates (P = 0.0022) and their MDP-stimulated isolated M phi population (P = 0.0004). However, patients with depressed PHA responses could have either normal or depressed T-cell proliferation in an anti-CD3-, anti-CD4-stimulated system. If APC-independent T-cell proliferation was depressed, induced IL-10 levels were suppressed (P = 0.007). However, if APC-independent T-cell proliferation was normal or elevated, IL-10 levels could be normal or elevated (P = 0.018). Decreased IL-10 levels correlated with depressed mitogen responses and depressed T-cell proliferation. IL-10, therefore, could not be inducing trauma patients' immunosuppression. Patients with elevated M phi TNF-alpha levels had depressed M phi IL-10 levels.

Continued tumor necrosis factor receptor expression by trauma patients' monocytes (Mphi) despite TNF alpha secretion.

In investigating various mechanisms for continued elevated tumor necrosis factor alpha (TNF alpha) production in trauma patients' monocytes (Mphi), we examined TNF receptor (TNFR) levels on the patients' Mphi as a possible altered pathway leading to continued autocrine TNF alpha stimulation. Mphi TNFR synthesis and shedding are both increased as TNF alpha protein production increases. In fatal meningococcal infections, TNFR shedding fails to pace TNF alpha production. Here, isolated normal and trauma patients' Mphi (injury severity score greater than 30), were examined by flow cytometry using phycoerythrin-labeled TNF alpha to detect increased or decreased TNFR expression concomitant to Mphi production of secreted TNF alpha (as measured in the LM bioassay). Immunoaberrant patients (mitogen proliferation depressed) had reduction in detectable TNF alpha binding by their TNFR, while Mphi from immunocompetent (normal mitogen response) trauma patients' Mphi had a TNFR expression intensity comparable to normals' Mphi. Upon in vitro stimulation of TNF alpha (IFN gamma + muramyl dipeptide) normals' and immunocompetent patients' MO TNFR expression is decreased for the entire 18 h period during which secreted TNF alpha is produced, but immunoaberrant trauma patients' Mphi increased their TNFR expression, while concomitantly producing both secreted and cell-associated TNF alpha protein. Patients' Mphi with highly elevated TNF alpha levels are still expressing high levels of TNFR and capable of auto-stimulating TNF alpha production. This elevated TNFR expression could be due to reduced shedding, overproduction of TNFR, or both.

Dibutyryl-cAMP modulation of receptor expression and antigen presentation capacity in monocyte subpopulations.

Monocyte phenotype heterogeneity is often associated with functional differences between the distinguished Mphi subpopulations. We have previously demonstrated that the Mphi subpopulation separated and stimulated by rosetting Mphi via the Type I Fc gamma R (CD64) are poor antigen presenting cells but can be induced to greater production of TNF alpha, IL-6 and PGE2 than the Fc gamma RI- Mphi population. Here we demonstrate that the Fc gamma RI- Mphi represent the major antigen presenting Mphi population and that APC capacity of the FcRI- Mphi can be further increased by elevating intracellular cAMP levels. Treatment of the Fc gamma RI+ Mphi with db cAMP decreases both their expression of CD64 and their capacity to produce TNF alpha to the levels typical of Fc gamma RI- Mphi. Db cAMP treatment of the Fc gamma RI+ Mphi subpopulation, however, cannot augment the antigen presenting capacity of this low APC Mphi subpopulation to the level of that of the Fc gamma RI- Mphi. Basal expression of the Mo3 activation marker was comparable in the FcRI+/FcRI- Mphi subpopulations, but the FcRI+ Mphi were induced by db cAMP treatment to increase their Mo3 expression to higher levels than the FcRI- Mphi. These results suggest that although elevated intracellular cAMP levels can modulate some Fc gamma RI+ Mphi functions to more closely parallel those of the Fc gamma RI- Mphi, this treatment cannot increase the efficiency of the Fc gamma RI+ Mphi subpopulation as an antigen presenting cell.

Differential induction of human monocyte transforming growth factor beta 1 production and its regulation by interleukin 4.

We have previously shown that trauma patients' monocytes which are in vivo activated by multiple injury-induced mediators have elevated transforming growth factor-beta (TGF beta) bioactivity. Interleukin-4 (IL-4), a Th2 and B lymphocyte stimulatory factor, has been shown to inhibit monocyte production of a number of mediators both after lipopolysaccharide stimulation and after trauma-induced stimulation. However, IL-4 inhibitory effects appears to vary, depending on the mixture of inducing stimuli. Here we describe the in vitro IL-4 inhibition of human monocyte TGF beta bioactivity using several stimulation induction protocols: muramyl dipeptide stimulation alone, or after Fc gamma RI (CD64) cross-linking induction, interferon-gamma (IFN gamma) priming, or trauma-generated in vivo mediator induction. IL-4 suppressed both muramyl dipeptide-induced TGF beta bioactivity and TGF beta mRNA in a dose-dependent fashion and was most effective when IL-4 was administered at initiation of normal monocyte stimulation. Muramyl dipeptide (MDP)-induced increases in trauma patients' monocyte TGF beta bioactivity were also inhibited by high doses of IL-4 (25 ng/ml). Fc gamma RI cross-linking increased MDP-induced normal monocyte TGF beta bioactivity, but this increase could be consistently inhibited only by very high IL-4 concentrations (50 ng/ml). IL-4 did not consistently downregulate MDP-induced TGF beta bioactivity in IFN gamma-primed monocytes. IL-4 can suppress monocyte TGF beta production, as well as other monocyte mediators, but its efficiency depends on the stimuli combination present in the microenvironment.

Elevated monocyte interleukin-6 (IL-6) production in immunosppressed trauma patients. II. Downregulation by IL-4.

Aberrant monocyte mediator production is pivotal in the development of posttrauma immunosuppression. We have previously shown that immunodepressed trauma patients' monocytes produce elevated interleukin-6, suggesting their in vivo preactivation. This study confirms that preactivated patients' Mø produce greater levels of IL-6 than normals' Mø to the same in the in vitro Fc gamma RI stimulation. We also demonstrate the capacity of interleukin-4 to downregulate the elevated interleukin-6 production of trauma patients' in vivo preactivated monocytes. Monocyte interleukin-6 downregulation by interleukin-4 is dose dependent and occurs whether Fc gamma RI cross-linking, muramyl dipeptide, indomethacin plus muramyl dipeptide, or interferon-gamma plus muramyl dipeptide is the interleukin-6 inducing stimulus. Furthermore, interleukin-4-dependent downregulation of monocyte interleukin-6 expression is confirmed at both the supernatant and the mRNA levels. Simultaneous downregulation of posttrauma elevated monokines implies a possible therapeutic benefit of interleukin-4 for trauma patients.

Elevated monocyte interleukin-6 (IL-6) production in immunosuppressed trauma patients. I. Role of Fc gamma RI cross-linking stimulation.

This study demonstrates that immunodepressed trauma patients' monocytes produce elevated interleukin-6 to adherence, bacterial, and cytokine stimulation compared to immunocompetent trauma patients' or normals' monocytes, suggesting their in vivo preactivation possibly mediated by the hyperimmunoglobulinemia which characterizes these patients. Furthermore, stimulation of monocytes through cross-linking their Fc gamma RI induces and augments interleukin-6 (IL-6) production to subsequent stimulation both in trauma patients' (P less than 0.001) and in normals' (P less than 0.001) monocytes. As we reported earlier, immunodepressed trauma patients have an increased proportion of Fc gamma RI-bearing monocytes in their total monocyte population and here we show that those Fc gamma RI+ monocytes produce significantly elevated interleukin-6, suggesting a relationship between elevated monocyte interleukin-6 production and Fc gamma RI triggering. Interleukin-6 induction by FcRI stimulation is not mediated solely by FcRI-induced M phi tumor necrosis factor alpha, IL-1 alpha, or IL-1 beta production and is independent of M phi prostaglandin E2 levels. Therefore, FcRI stimulation-induced elevated M phi IL-6 might contribute to the increased immunoglobulin levels posttrauma.

Role of elevated monocyte transforming growth factor beta (TGF beta) production in posttrauma immunosuppression.

We previously reported that increased production of prostaglandin E2 by monocytes is a pivotal mechanism in posttrauma immunopathology. Here we characterize monocyte levels of transforming growth factor beta and examine the effects of elevated transforming growth factor beta on prostaglandin E2 release by patients' monocytes. Trauma patients' and normals' monocyte supernates (+/- stimulation with muramyl dipeptide) were acid treated and assayed for transforming growth factor beta using the mink lung-cell bioassay. Alternatively, human transforming growth factor beta was added to patients' and normals' monocytes and prostaglandin E2 production assayed. Significantly elevated transforming growth factor beta levels (median = 181.7 pmol/10(6) monocytes) were detected in immunosuppressed patients' monocytes but not immunocompetent trauma patients' (median = 32.0 pM) or normals' (median = 20.4 pM) monocytes. Adding transforming growth factor beta to monocytes resulted in a significant elevation of prostaglandin E2 levels. Elevated monocyte transforming growth factor beta levels in trauma patients could be both suppressing T-lymphocyte functions and maintaining elevated monocyte prostaglandin E2 synthesis.

Aberrations in post-trauma monocyte (MO) subpopulation: role in septic shock syndrome.

Appearance of increased proportions of monocytes bearing the 72kd(FcRI) receptor for IgG correlated to aberrant monocyte (MO) functions, depressed immune functions, and poor clinical outcome. The trauma patients' FcRI+ MO subpopulation produced the majority of their elevated IL-6, TNF alpha, TGF beta, and PGE2. IgG stimulation of patients' MO through FcRI not only stimulated TNF alpha, IL-6, and PGE2 levels, but also greatly augmented the levels of these monokines produced after subsequent bacterial challenge. Post-trauma increased IL-6 levels can lead to polyclonal B-cell activation and high levels of circulating, nonspecific IgG as seen in trauma patients. This nonspecific IgG triggers the FcRI on the increased numbers of FcRI+ MO leading to ever-increasing monokine levels. IL-4 was found to downregulate patients' FcRI+ MO production of mediators. The cycle of altered cytokine levels, increased FcRI+ MO numbers, elevated IgG, and augmented triggering of FcRI+ MO may be broken by addition of IL-4.

Induction and regulation of monocyte procoagulant activity.

Monocyte (MO) procoagulant activity (PCA) is induced by various stimuli including allogeneic stimulation, immunocomplexes, and bacterial products. Antigen-antibody complex stimulation therefore represents a pathway for MO PCA induction. Activation of MO PCA has been demonstrated in immunocomplex disease and could represent a major pathology in transplanted immunocomplex disease patients. Stimulation of monocytes via their FcRI receptor has been demonstrated to induce TNF and PGE2. This report demonstrates that stimulation of the high-density FcRI receptor-bearing (FcRI+) MO by resetting with anti-Rh coated erythrocytes also induces significant PCA levels (P less than 0.001). Muramyl dipeptide (MDP), a Gram-positive bacterial cell wall analogue, further increased PCA levels in the FcRI stimulated MO subpopulation (P less than 0.003). Although increased PCA levels were also induced in the FcRI- MO subpopulation by MDP (P less than 0.003), the FcRI+ MO responded with much greater levels of PCA and PGE2 (P less than 0.001). Greater PCA levels in the FcRI-positive MO subpopulation may indicate that stimulation of MO through their FcRI represents a different pathway from allogenic PCA activation, which can be augmented by subsequent bacterial challenge. A novel inhibitory effect of IL-4 on MO PCA induction is also demonstrated. IL-4 downregulated MO PCA levels either after isolation stimulation (55 +/- 19%), FcRI stimulation (57 +/- 12%), or FcRI plus MDP stimulation (60 +/- 13%). PCA and PGE2 levels were concomitantly downregulated by IL-4 both in the FcRI-stimulated, FcRI+ and in the MDP-stimulated FcRI- MO subpopulations. Since indomethacin blocked MDP induced MO PGE2 production without affecting MO PCA levels, PGE2 production is not required for FcRI-stimulated PCA induction.

Differential tumor necrosis factor production by human monocyte subsets.

The human monocyte (M phi subset rosetting with anti RH-coated human erythrocytes via high-affinity, 72 kD receptors (FcRI+), contains the PGE2-producing immunosuppressive subpopulation, while the non-rosetting M phi subset (FcRI-) is the major plasminogen activator-producing and antigen-presenting M phi. This study gives additional evidence for the functional disparity of the FcRI- and FcRI+ M phi subsets. We are demonstrating that the normal human M phi subset isolated by rosetting via the FcRI receptor (FcRI+) produces greater quantities of tumor necrosis factor (TNF) than the non-rosetting (FcRI-) M phi. TNF production by the FcRI+ M phi subset is greater than that of the FcRI- M phi subset whether secreted (P less than .001) or cell-associated (P less than .001) TNF is assessed. The rosetting M phi subset that expresses high densities of FcRI (FcRI+) produced the majority of normal human peripheral blood M phi TNF whether the stimulation was an interferon gamma (IFN gamma) prime followed by MDP or followed by interleukin-2 (IL-2). The Fc rosetting technique itself resulted in some TNF induction in the FcRI+ M phi subset accounting for some of the increased TNF production of this subset. However, increasing the stimulation level of the FcRI very-low-density (FcRI-) M phi subset did not induce it to produce TNF levels equivalent to the moderately stimulated FcRI+ M phi subset. These data, therefore, imply that only stimulation through the type I Fc gamma receptor can augment or induce TNF activity. The difference in the M phi subset's TNF response remained even after the FcRI- M phi subset received a 2.5-fold increase in stimulation with the classical M phi induction regimen of IFN gamma plus bacterial cell wall product. Although stimulation of the FcRI+ M phi subset via crosslinking of their FcRI receptors might represent a unique TNF stimulation pathway, this stimulation does not occur in the low-density FcRI (FcRI-) M phi subset, again indicating functional disparity between these subsets. Greater TNF production by the FcRI+ M phi subset was induced concomitant to elevation of its prostaglandin E2 production. Since both TNF and PGE2 are increased in some patient groups, a pathological shift in the FcRI+ versus FcRI- M phi ratio in these patients coupled to the functional differences in FcRI+ and FcRI- M phi subsets could be one mechanism for the development of immunoincompetence.

Mechanisms of altered monocyte prostaglandin E2 production in severely injured patients.

Monocytes from immunosuppressed trauma (11 patients) and burn (12 patients) patients stimulated with muramyl dipeptide, a potent prostaglandin E2 (PGE2) secretagogue, showed twofold greater PGE2 production compared with normal controls or immunocompetent patients. Monocyte plasminogen activator production was markedly depressed and inversely correlated to patients' monocyte hyper PGE2 production. Levels of the PGE2-producing monocyte subset (selected as high-affinity Fc+ receptors) were progressively elevated after injury in immunosuppressed patients, reaching 65% to 80% of the total monocyte population (39% for normal controls). Although early T-suppressor (Ts) lymphocytes did not augment monocyte PGE2 secretion, Ts lymphocytes that appeared late (greater than 12 days after injury), during chronic infection, acted as monocyte PGE2 secretagogues. Posttraumatic increases in monocyte sensitivity to PGE2 secretagogues augmented the numbers of PGE2-secreting monocytes, and the appearance of Ts lymphocytes with PGE2 secretagogue activity may be responsible for elevated monocyte PGE2 production in immunosuppressed trauma patients.