Regulation of secretion of IL-4 and IgG1 isotype by melatonin-stimulated ovalbumin-specific T cells

In the present study, we describe the potential role of melatonin, a pineal hormone, in regulating the activation of the antigen-specific T cell response. Melatonin encouraged the proliferation of Th cells and improved their ability to secrete IL-4, but down-regulated the levels of IL-2 and interferon-gamma (IFN-γ). Melatonin, however, could not exert any influence on the T cells of unprimed mice. On studying the regulation of subclass of IgG isotype, melatonin specifically enhanced the secretion of antigen-specific IgG1 antibodies and decreased the yield of IgG2a isotype. The results suggest that melatonin possibly acts by selectively activating a Th2-like immune response.     

Differential regulation of Th1 and Th2 cells by p91–110 and p21–40 peptides of the 16-kD α-crystallin antigen of Mycobacterium tuberculosis

Permissively recognized peptides which can activate lymphocytes from subjects with a variety of class II HLA types are interesting diagnostic and vaccine candidates. In this study we generated T helper clones reactive to the permissively recognized p21–40 and p91–110 peptides of the 16-kD heat shock protein of Mycobacterium tuberculosis. All the clones specific for p91–110 secreted interferon-gamma (IFN-γ) and were of the Th1 phenotype. By contrast, the p21–40 peptide favoured the generation of IL-4-producing clones. Antibody blockade established that the peptide-specific Th clones could either be DR-, DP- or DQ-restricted. Thus, two permissively recognized sequences p21–40 and p91–110 from the same mycobacterial antigen can drive the differentiation of functionally distinct T helper subsets. Attempts to immunize against tuberculosis should bear in mind epitope specificity if a favourable Th subtype response is to be generated.     

Potential role of B7-1 and CD28 molecules in immunosuppression in leprosy

In order to understand the mechanism of unresponsiveness towards Mycobacterium leprae antigens in leprosy, we evaluated the role of M. leprae sonicate antigens in regulating the expression of the costimulatory molecules B7-1, CD28, intercellular adhesion molecule-1 (ICAM-1), LFA-1α, LFA-1β and Mac-1 on the lymphocytes of both leprosy patients and healthy subjects. It was observed that the expression of B7-1 and CD28 was significantly decreased but the levels of ICAM-1 and LFA-1α were increased in patients with untreated borderline leprosy (BL)/lepromatous leprosy (LL) disease. No remarkable change was noticed in the case of borderline tuberculoid (BT) leprosy or treated BL/LL patients. Further, a striking finding was that lymphocytes from healthy subjects cultured with a particularly high dose of M. leprae sonicate antigens down-regulated the expression of B7-1 and CD28 molecules, but up-regulated the display of ICAM-1 and LFA-1α. Furthermore, proliferation induced by M. leprae sonicate was inhibited only by anti-B7-1 antibody. Mycobacterium leprae antigen-induced suppression of the proliferation of lymphocytes of healthy volunteers and LL patients was reversed by culturing the lymphocytes with purified protein derivative (PPD). It may be concluded from the findings in this study that down regulation of B7-1 and CD28 in BL/LL leprosy patients may be responsible for a defective T cell signalling by the B7-1/CD28 pathway caused by M. leprae antigens. This may lead to clonal inactivation of M. leprae-reactive T cells, consequently the bacilli grow without restriction in macrophages.     

CD4+ T-cell memory: generation and multi-faceted roles for CD4+ T cells in protective immunity to influenza

Summary: We have outlined the carefully orchestrated process of CD4⁺ T‐cell differentiation from naïve to effector and from effector to memory cells with a focus on how these processes can be studied in vivo in responses to pathogen infection. We emphasize that the regulatory factors that determine the quality and quantity of the effector and memory cells generated include (i) the antigen dose during the initial T‐cell interaction with antigen‐presenting cells; (ii) the dose and duration of repeated interactions; and (iii) the milieu of inflammatory and growth cytokines that responding CD4⁺ T cells encounter. We suggest that heterogeneity in these regulatory factors leads to the generation of a spectrum of effectors with different functional attributes. Furthermore, we suggest that it is the presence of effectors at different stages along a pathway of progressive linear differentiation that leads to a related spectrum of memory cells. Our studies particularly highlight the multifaceted roles of CD4⁺ effector and memory T cells in protective responses to influenza infection and support the concept that efficient priming of CD4⁺ T cells that react to shared influenza proteins could contribute greatly to vaccine strategies for influenza.     

Novel lectins from rhizomes of two Acorus species with mitogenic activity and inhibitory potential towards murine cancer cell lines

Two novel lectins were purified from rhizomes of two sweet flag species, namely Acorus calamus (Linn.) and Acorus gramineus (Solandin Ait.) by affinity chromatography on mannose linked epoxy-activated Sepharose 6B. The apparent molecular mass of the lectins, as determined by gel filtration chromatography, was 56 kDa for ACL and 55 kDa for AGL. In SDS-PAGE, pH 8.3, both lectins migrated with a subunit molecular mass of 13.6 kDa and 13.5 kDa, respectively, under reducing and non-reducing conditions thus indicating the absence of disulphide linkages. Acorus lectins readily agglutinated rabbit, rat and guinea pig erythrocytes. Both ACL and AGL also reacted with RBCs from sheep, goat and human ABO blood groups after neuraminidase treatment. ACL and AGL were inhibited by mannose/glucose and their derivatives. The most effective inhibitor was methyl-alpha-D-mannopyranoside. Acorus lectins were stable up to 55 degrees C, did not require metal ions for their activity and were also affected by high concentrations of denaturants like urea, thiourea and guanidine-HCl. These lectins showed potent mitogenic activity towards mouse splenocytes and human lymphocytes. Both ACL and AGL also significantly inhibited the growth of J774, a murine macrophage cancer cell-line and to lesser extent WEHI-279, a B-cell lymphoma.     

Calculation of antibody and antigen concentrations from ELISA data using a graphical method.

A graphical method for determining the concentration of either the antibody or the antigen from ELISA data is presented in the form of a GWBASIC program. In the program, ELISAEQ, optical densities (OD) obtained from a 96-well ELISA plate can be input either directly by interfacing a microplate reader to the computer or manually. The program uses standard sample data, and selects the semilogarithmic linear range. Over this range, a least-squares method is used to determine the concentrations of interest. In addition, a hyperbolic interpolation formula is derived over the entire range for estimating the antibody or antigen concentration of the unknown samples whose OD is beyond the linear range.     

Melatonin reversal of lipopolysacharides-induced thermal and behavioral hyperalgesia in mice

The perception of pain sensation (threshold), whether local or central, is altered by inflammatory processes. Anti-inflammatory drugs block this by raising the pain threshold and by reducing the inflammatory process. Melatonin is claimed to have anti-inflammatory activity in animal models of acute and chronic inflammation. However, it is not known whether melatonin can reverse the hyperalgesia that is secondary to the inflammation. The present study aimed to assess the modulatory effect of melatonin on lipopolysaccharides-induced alteration of pain perception in mice. Central perception of pain was assessed with the tail-flick and hot-plate methods and local hyperalgesia was assessed by noting the animal's reactions such as paw licking and rearing after the intraplantar injection of lipopolysaccharides (5 microg/paw). Local administration (intraplantar) of lipopolysacharides induced hyperalgesia when measured by both central effects and behavioral reactions. Melatonin (5 and 10 mg/kg), like dexamethasone (0.5 mg/kg), given 30 min prior to, and 4 and 8 h after lipopolysaccharides (5 microg/paw) challenge attenuated central and behavioural hyperalgesia. The attenuation of lipopolysaccharides-induced hyperalgesia by melatonin was not reversed by naltrexone (4 mg/kg). In vitro studies showed that melatonin, in concentrations ranging from 100 to 1000 nM, suppressed tumor necrosis factor-alpha (TNF-alpha) without affecting the nitric oxide (NO) release in lipopolysaccharides-activated murine peritoneal macrophages. Taken together, the present results demonstrated that melatonin reverses lipopolysaccharides-induced hyperalgesia.     

Understanding the biology of 16 kDa antigen of Mycobacterium tuberculosis: scope in diagnosis, vaccine design and therapy

Heat shock proteins (HSPs) are conserved and ubiquitous house keeping entities that act as molecular chaperones, which protect the cell from damage during stress. One such HSP, the 16 kDa antigen, from Mycobacterium tuberculosis (Mtb) has received considerable attention due to its importance in tuberculosis latency and immunodominant property. In this article, we discuss about the potential role of 16 kDa antigen of Mtb in latency, its expression, regulation, and implication in host immune response. We also highlight the scope of employing 16 kDa in early diagnosis, development of vaccine and as a potential drug target.