Serum IL-1ra is elevated in lepromatous leprosy patients.

Patterns of production of specific cytokines are accepted as standards for T-lymphocyte subsets in diseases caused by intracellular parasites. These lymphocyte subsets (Th1 and Th2) have been associated with the different poles of the leprosy spectrum. Lepromatous leprosy (LL) onset correlates with cytokines produced by Th2 cells on the grounds of the patient's poor cellular immune response, i.e., interleukin 2 (IL-2) and gamma interferon (IFN-gamma) deficiency. On the other hand, tuberculoid leprosy (TL) has been associated with a Th1 response. Moreover, pro-inflammatory cytokines like IL-1 beta and tumor necrosis factor-alpha (TNF-alpha) play a major role in chronic inflammatory pathologies being IL-1ra and TNF-alpha soluble receptors, natural counterbalancing inhibitors. In light of this background, we decided to measure serum levels of IL-1 beta, IL-1ra, TNF-alpha and IL-6 in LL and TL patients, and we also studied the production in vitro of Th1 (IFN-gamma, IL-2), Th2 (IL-4, IL-10) and TNF-alpha cytokines. Our data showed that IL-1ra is highly elevated in sera from LL patients; there were no differences in Th2 cytokine levels and there were diminished levels in Th1 cytokines.

Addiction of anti-CD28 antibodies restores PBMC proliferation and IFN-gamma production in lepromatous leprosy patients.

During antigen recognition, T lymphocytes are primed by a physical interaction with antigen-presenting cells (APC). At least two signals are needed to activate T cells. One is provided by T cell receptor (TCR)/CD3 in the context of the mayor histocompatibility complex (MHC), and another signal is mediated by antigen-independent molecules, that is T cell membrane-bound CD28 and its specific ligand B7-1 (CD80) present in APC. Both signals trigger a series of metabolic events initiating right at the cell membrane and ending with activation and proliferation of T cells as well as specific cytokines synthesis. Our main goal was to determine whether deficiency in interferon-gamma (IFN-gamma) production shown by peripheral blood mononuclear cells (PBMC) from lepromatous leprosy (LL) patients, could be overcome by reconstituting in vitro the appropriate signals (by means of addition of anti-CD28 and anti-CD80 monoclonal antibodies). We also determined the stimulation index (SI) in the same PBMC. Our results demonstrated no significant differences in CD80 expression monocytes and B lymphocytes from LL patients when compared with healthy subjects. Nonetheless, CD28 expression significantly decreased in lymphocytes from LL patients (p < 0.01). Regarding IFN-gamma levels and SI, LL-PBMC failure before mitogenic stimuli could be reversed by further incubation with anti-CD28 antibody, but stimulation by specific antigen of Mycobacterium leprae was not changed. Addition of anti-CD80 antibody significantly increased IFN-gamma levels in phytohemagglutinin (PHA)-stimulated PBMC, although proliferation deficiency persisted. Cells stimulated with specific antigen did not modify either their proliferation or IFN-gamma levels.

Recognition of Mycobacterium leprae antigens with antibodies present in sera from patients with lepromatous leprosy.

A great diversity of antigens from Mycobacterium leprae have been described. One practical approach should be to utilize them as markers to indicate when a household contact is at risk of becoming infected and then moving to an active form of leprosy. For this purpose, sonic extracts of M. leprae were fractionated in 10% SDS-PAGE under reducing conditions. The fractionated proteins were then transferred to nitrocellulose sheets and incubated with sera from lepromatous leprosy cases, their contacts, and normal subjects in order to reveal the frequency of antigen recognition of each set of sera. The results showed that sera from lepromatous leprosy patients frequently recognized two proteins, one of approximately 28 kDa and the other of approximately 65 kDa, when compared with the sera from normal subjects. The contacts frequently recognized an approximately 16-kDa antigenic band, while sera from normal subjects recognized one protein of approximately 18 kDa. According to the results, the four recognized proteins from M. leprae can be considered markers of the above conditions (approximately 65 kDa, approximately 28 kDa for lepromatous leprosy, approximately 16 kDa for contacts, and approximately 19 kDa for normal subjects). From these, an easy serological test, such as an ELISA, can be developed to predict if a contact is moving toward lepromatous leprosy before detection of the actual clinical signs or symptoms.