transforming-growth-factor-beta and Meningitis--Pneumococcal

For the past several years immunologists have been fascinated by a series of experiments showing that transforming growth factor beta (TGF beta) suppresses T- and B-lymphocyte growth as well as IgM and IgG production by B cells. Moreover, while exerting chemotactic activity on monocytes and inducing expression of interleukin-1 and interleukin-6 by these cells, TGF beta interferes with bacterially induced tumor necrosis factor alpha production, oxygen radical formation and the adhesiveness of granulocytes to endothelial cells. These mechanisms may provide the basis for the effect of TGF beta to prevent the microvascular changes associated with brain edema formation in bacterial meningitis. Given the potential of lymphocytes as well as macrophages to produce TGF beta 1, this cytokine may exert negative feedback signals on the immune response, provided the cytokine is processed from its latent form to the bioactive homodimer. Potent effects of TGF beta have been observed in experimental animals including the inhibition of the generation of virus-specific cytotoxic T cells and antiviral antibodies as well as the diminution of cellular infiltrates with decreased major histocompatibility complex class-II expression and CD8+ T cells in the tissue of virally infected animals. TGF beta may also be of importance in tumor immunology. By the production of bioactive TGF beta as detected in glioblastoma and acute T-cell leukemia, tumor cells may induce an immunodeficiency state and escape immune surveillance. In inflammation, monitoring of TGF beta in the tissue will bring light on the immune regulation in acute and chronic inflammatory diseases.

Topics: Animals; Astrocytoma; Autoimmunity; B-Lymphocytes; Brain Neoplasms; Cytokines; Humans; Immunoglobulins; Immunosuppression Therapy; Meningitis, Pneumococcal; T-Lymphocytes; Transforming Growth Factor beta

Topics: Child; Child, Preschool; Female; Humans; Infant; Infant, Newborn; Interleukin-10; Interleukin-6; Male; Meningitis, Bacterial; Meningitis, Haemophilus; Meningitis, Listeria; Meningitis, Pneumococcal; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha

IL-10, a potent immunosuppressive cytokine, leads to macrophage/monocyte deactivation, inhibiting the production of cytokines and the release of reactive oxygen species and reactive nitrogen intermediates, which are known to be involved in the pathophysiology of bacterial meningitis. We investigated the effect of IL-10 on regional cerebral blood flow, intracranial pressure, cerebrospinal fluid (CSF) white blood cell count, and brain water content within 6 h after intracisternal (i.c.) pneumococcal challenge in a rat model of meningitis. Compared with IL-10 vehicle-injected infected rats, i.p. administration of 5 microg of IL-10 significantly attenuated the increase in regional cerebral blood flow, brain water content, intracranial pressure, and CSF white blood cell count, whereas a lower dosage of IL-10 (0.5 microg) was ineffective. The inhibitory effect of IL-10 (5 microg) was observed irrespective of time of IL-10 administration: just before, 1 h after, or 4 h after pneumococcal challenge. In contrast, i.c. application of IL-10 (5 microg) did not modulate these pathophysiologic parameters, and even augmented CSF pleocytosis. Moreover, i.c. injection of IL-10 alone induced meningeal inflammation in uninfected rats. IL-10 injected i.p., but not i.c., markedly inhibited the increase in IL-6 levels, as determined in CSF of infected animals. IL-10 suppressed the increase of nitrite concentration in cell culture supernatant of primary rat cerebral endothelial cells when stimulated with heat-killed pneumococci. The possible modes of action of IL-10 in pneumococcal meningitis may involve its interference with the production of nitric oxide or IL-6.

Topics: Animals; Astrocytes; Body Water; Brain; Cerebrospinal Fluid; Cerebrovascular Circulation; Disease Models, Animal; Endothelium, Vascular; Injections, Intraperitoneal; Injections, Spinal; Interleukin-10; Interleukin-6; Intracranial Pressure; Leukocyte Count; Male; Meningitis, Pneumococcal; Nitric Oxide; Rats; Rats, Wistar; Transforming Growth Factor beta