Pharmacological Studies on Leaves of Withania somnifera.

Anti-inflammatory activity and protective effect against CCl (4)-induced hepatotoxicity of alcoholic extract of leaves of WITHANIA SOMNIFERA have been assessed. The leaves were found to possess marked effects in subacute inflammation and hepatotoxicity. A comparison of the anti-inflammatory properties revealed the extract at 1 g/kg dose to be as active as 50 mg/kg of phenylbutazone and 10 mg/kg of hydrocortisone. The protective effect of the extract at 1 g/kg dose against CCl (4)-induced hepatotoxicity was comparable to 10 mg/kg of hydrocortisone.     

Mechanisms of immunotherapeutic intervention by anti-CD154 (CD40L) antibody in high-risk corneal transplantation.

This study aimed to determine the effects of anti-CD154 on T cell cytokine profiles and ocular chemokine gene expression after high-risk corneal transplantation and to specifically determine if CD154 blockade is associated with a switch from a Th1 to a Th2 alloimmune response. Mice were used as recipients of syngeneic or multiple minor H or MHC antigen-mismatched corneal grafts. Recipient beds were neovascularized (high-risk). Hosts were randomized to receive either anti-CD154 antibody or control immunoglobulin (Ig) perioperatively. Two weeks after corneal transplantation, allospecific delayed-type hypersensitivity (DTH) was evaluated. Frequencies of interferon-gamma (IFN-gamma)-, interleukin-2 (IL-2)-, IL-4-, and IL-5-secreting T cells in the hosts were measured by enzyme-linked immunospot (ELISPOT) assay. Ocular chemokine gene expression in anti-CD154-treated and control hamster Ig-treated groups was determined using a multiprobe ribonuclease protection assay (RPA). Leukocyte infiltration of corneal grafts was evaluated microscopically. Anti-CD154-treated mice did not exhibit allospecific DTH. The frequencies of Th1 cytokine-producing but not Th2 cytokine-producing T cells were significantly reduced in anti-CD154-treated hosts. Postoperative mRNA levels of RANTES and macrophage inflammatory protein-1beta (MIP-1beta) in anti-CD154-treated eyes were substantially suppressed compared with hamster Ig-treated controls. Leukocyte infiltration was profoundly suppressed in grafts of anti-CD154-treated hosts. These data demonstrate that blockade of the CD40-CD154 costimulatory pathway after corneal transplantation inhibits Th1-mediated responses but does not induce a switch to a Th2-specific response. In addition, anti-CD154 therapy suppresses ocular chemokine gene expression and leukocytic infiltration into allografts.     

Molecular mechanisms of apoptosis in the cells of the immune system in human aging

Summary: Aging is associated with progressive decline in immune functions and increased frequency of infections, autoimmunity, and cancer. Among immune functions, a decline in T‐cell functions during aging predominates. In this review, I discuss the molecular signaling of three distinct pathways of apoptosis, namely the death receptor pathway, the mitochondrial pathway, and the most recently described endoplasmic reticulum stress pathway, and the relative sensitivity of naïve, central memory, and effector memory CD8⁺ T‐cell subsets to apoptosis. In addition, I review apoptosis, especially via death receptor pathway, in naïve and various memory subsets of CD4⁺ and CD8⁺ T cells (with primary emphasis on CD8⁺ naïve and memory subsets) in human aging and discuss the role of apoptosis in immune senescence.     

P-glycoprotein (MDR 1 gene product) in cells of the immune system: Its possible physiologic role and alteration in aging and human immunodeficiency virus-1 (HIV-1) infection

P-glycoprotein, a 170-kd glycoprotein encoded by theMDR 1 gene, is a member of a highly conserved superfamily of ATP-binding cassette (ABC) transport proteins. It shares extensive homology with numerous bacterial and eukaryotic ABC transport proteins. P-glycoprotein acts as an energy-dependent efflux pump that appears to transport structurally diverse agents ranging from ions to peptides. P-glycoprotein (P-gP) has been implicated as playing a role in multidrug (MDR) resistance in cancer, chloroquine-resistantPlasmodium falciparum infection, and possibly human immunodeficiency virus-1 (HIV-1) resistance to nucleoside compounds. A number of normal tissues in humans and rodents have been shown to express high levels of P-gp. The expression and function of P-gp in cells of the immune system have been explored in the past 2 years. This review presents a state of the art regarding the expression, regulation, and function of Pgp in cells of the immune system. In addition, its alteration in aging and HIV-1 infection is reviewed. A possible physiologic role of P-gp in cytokine secretion, antigen processing/presentation, and effector functions is also discussed.     

Human immunodeficiency virus-associated changes in signal transduction

It is well established that the activation of T lymphocytes by mitogen/antigen is accompanied by a rise in intracellular free calcium ([Ca²⁺]_i), changes in membrane potential, metabolism of inositol phospholipid, and activation of protein kinase C. Theseearly events of signal transduction culminate inlate events of lymphocyte activation, namely, DNA synthesis, lymphokine production, and cellular proliferation. In this study we examined the effect of human immunodeficiency virus (HIV) on changes in membrane potential and [Ca²⁺]_i levels. The membrane potentials were markedly decreased (depolarized) in T cell lines infected with HIV (H9/HTLV IIIb) and did not respond normally to phytohemagglutinin (PHA) or anti-T3 (anti-CD3) monoclonal antibody compared to uninfected H9 cell line. The basal [Ca²⁺]_i levels in H9/HTLV IIIb cells were increased in comparison to those in H9 cells; however, there was very little further increase in [Ca²⁺]_i in H9/HTLV IIIb cells following activation with PHA or anti-T3 monoclonal antibody. This is in contrast to a significant rise in [Ca²⁺]_i in H9 cells following similar stimulation. These data demonstrate abnormalities in the plasma membrane potential and [Ca²⁺]_i levels in chronically infected T cells with HIV. These abnormalities in signal transduction of the T-cell activation pathway could be responsible for T-cell dysfunction in patients with HIV infection.     

Humoral immunity in experimental immune carditis

An experimental model of carditis has been produced in the rhesus monkey by giving 12 weekly injections of a streptococcal membrane antigen. There was histological evidence of focal myocarditis, subendocardial infiltration with lymphomononuclear cells and in one animal myocardial granuloma formation. No valvular lesions were seen. Humoral immune responses monitored throughout the experiment showed that anti-heart antibodies appeared in circulation after the 2nd injection, attained maximal titres by the 6th injection, and thereafter the titres declined. The anti-membrane antibodies appeared slightly later and these titres kept rising till sacrifice. By the 6th injection there was evidence of complement consumption and appearance of circulating immune complexes. It is concluded that these immunological responses might have a role to play in the pathogenesis of carditis.     

Astrocytes and intracerebral immune responses

The astrocyte is the most abundant cell within the central nervous system (CNS). This cell subserves a multiplicity of important functions that contribute to the process of neural development as well as to the integrity of normal brain function. Adding to the already exhaustive list of capabilities, the astrocyte has now been demonstrated to function as an intracerebral antigen presenting cell. These findings are serving to revise our view of the brain as an immunoprivileged site and perhaps will shed some light on the pathogenetic mechanisms involved in a number of CNS disorders of immune dysregulation. In this review we provide some perspective on the regulatory mechanisms that influence astrocyte immune functions. Specifically, we address the role played by the major histocompatibility complex (MHC) antigens as well as adhesion molecules in the initiation of brain immune responses.