Transforming growth factor-beta does not alter interleukin-1 expression in cultured human macrophages

T-helper-1 and T-helper-2 responses in psychiatric disorders

The expanding field of psychoneuroimmunology has markedly increased knowledge about the interference of the central nervous system and the immune system. Immunological abnormalities in psychiatric patients have been repeatedly described in the last century. Modern concepts of immunology and the growing knowledge of psychoneuroimmunology may help in understanding the distinct immunological mechanisms in psychiatric disorders. One of these concepts regarding the adaptive immune system is the discrimination between Th1-like cell-mediated and Th2-like antibody-related immune responses. This article systematically describes alterations of Th1- or Th2-specific parameters in the major psychiatric disorders schizophrenia, major depression, and Alzheimer's disease. There are several hints of associations of these two distinct arms of immune response with subgroups of schizophrenia and major depression. The immunological research in Alzheimer's disease has already led to a preclinical model of immunotherapy. Categorization of immune parameters may also help to identify a possible immune-related pathophysiology in psychotic and affective disorders, resulting in specific treatment strategies.

Modulation of macrophage function by transforming growth factor beta, interleukin-4, and interleukin-10

The findings reviewed above leave no doubt as to the complexity of actions of TGF-beta, IL-4, and IL-10 on monocytes/macrophages. Along with MDF, whose actions were recently reviewed elsewhere, TGF-beta, IL-4, and IL-10 are the only presently known, purified cytokines that have been shown to have strong macrophage-deactivating effects. However, none of them can be categorized as purely macrophage deactivating since they also exert macrophage-activating effects. In vitro, their effects, both in terms of extent and direction (activating vs. deactivating), are strongly influenced by the stimulation conditions (e.g., triggering signal, cytokine concentration, timing of cytokine addition), the species (mouse vs. human), the source (blood vs. peritoneal, alveolar, colostral) and the state of differentiation/activation of the macrophage (e.g., resting vs. inflammatory). In addition, TGF-beta, as well as IL-4 and IL-10, up- and/or downregulates the function of several cell types other than macrophages, which further hampers our ability to predict, on the basis of in vitro experiments with macrophages, possible effects during an immune response in vivo. Despite this complexity, the highly reductive approach of in vitro studies has revealed important differences in the ability of TGF-beta, IL-4, and IL-10 to modulate the phenotype of monocytes/macrophages. The disparities have been most striking with regard to the secretory function of monocytes/macrophages (see Table 2). First, TGF-beta, IL-4, and IL-10 have a different spectrum of activity. Thus, TGF-beta, but not IL-4 or IL-10, can induce resting human monocytes to produce TNF, IL-1, and IL-6. Second, they affect monokine and RNI and ROI production to a different extent. For example, IL-10 is an approximately 25-fold more potent suppressor of LPS-induced TNF production by mouse macrophages than is TGF-beta. Third, they differ in their ability to overcome additional activating stimuli, so that in the presence of LPS, IL-4, but not TGF-beta or IL-10 suppresses IFN gamma-induced RNI release. Fourth, their macrophage-deactivating effects require different stimulation conditions. Thus, IL-4, but not TGF-beta, interferes with RNI release strongly only after preincubation of the macrophages. Finally, these agents deactivate macrophages by distinct mechanisms. For example, IL-10 causes massive downregulation of TNF mRNA, whereas TGF-beta suppresses TNF release on a translational level. It will be a challenge to define clinical applications for these potent macrophage modulators on the basis of their different spectrum of activities. For TGF-beta and IL-4 such studies have already been initiated.

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.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.