The effect of antigen presenting cells on the cytokine profiles of stable and reactional lepromatous leprosy patients.

In view of varied reports on the Th1/Th2 paradigm in leprosy, we used a novel real time (RT) fluorogenic reverse transcriptase based PCR (RT-PCR) to measure cytokine expression in peripheral blood cells from lepromatous leprosy patients with stable disease and those suffering from erythema nodosum leprosum (ENL/Type II) reactions. To evaluate the role of accessory cells in Th cell differentiation, co-expression of Th cytokines interferon gamma (IFNgamma) and interleukin (IL) 4 and regulatory cytokines IL 10 and IL 12 was compared in antigen stimulated peripheral blood mononuclear cells (PBMC), cultures containing T cells reconstituted with autologous monocytes (MO) and cultures containing T cells reconstituted with autologous dendritic cells (DC). 7/8 stable lepromatous leprosy patients showed co-expression of both IFNgamma and IL 4, suggesting a Th0 or a combination of Th1 + Th2 subsets in PBMC. The RT-PCR demonstrated that stable lepromatous patients and patients in ENL had significantly higher levels of IFNgamma mRNA molecules compared to IL 4. In fact, 5/8 ENL patients had undetectable levels of IL 4 mRNA, with a skewing of the cytokine response towards a Th1-like profile. Consistent with this. IL 12p40 mRNA molecules were significantly higher in the PBMC of ENL patients compared to stable lepromatous patients (P < 0.01). Reconstitution of purified T cells with autologous DC and MO from the stable lepromatous group resulted in down regulation of IL 4 (P < 0.03 for DC and P < 0.02 for MO) and IL 10 (P < 0. 01 for DC and P < 0.02 for MO), and a consequent skewing towards a Th1 profile similar to that seen in ENL patients. The fact that accessory cells could alter the cytokine profile in the reconstituted cultures suggests that they may play a role in determining Th subset differentiation in chronic diseases, and may influence the immunological stability of such diseases.

Dysregulation of IL-4 expression in lepromatous leprosy patients with and without erythema nodosum leprosum.

In order to increase our understanding of the immunological basis of erythema nodosum leprosum (ENL), we studied Th-like cytokine profiles in 130 leprosy patients, employing both the conventional and a novel, real-time, fluorogenic reverse transcriptase-based PCR (RT-PCR). The concomitant expression of both Th-like cytokines, interferon-gamma and IL-4, and the regulatory cytokines, IL-10 and IL-12, was studied in the peripheral blood cells of leprosy patients with and without ENL. In the conventional RT-PCR, varied cytokine profiles were observed in individual patients of all clinical types. Fifty-three percent of lepromatous patients without ENL and 59% of tuberculoid leprosy patients showed co-expression of IFN gamma and IL-4, indicating a non-polarized Th 0 pattern. Of the 36 patients with ENL, 58% demonstrated a polarized Th 1 pattern, with only 30% expressing both cytokines. Semiquantitative RT-PCR indicated a lower expression of IL-4 compared to that of IFN gamma in the lepromatous patients without ENL; the difference was even greater among those with ENL. The sensitive, real-time PCR confirmed the down-regulation of IL-4 and IL-10, with absence of IL-4 in half of the patients, resulting in skewing of the cytokine response toward a Th 1-like profile.

Antisphingolipid antibodies in the sera of leprosy patients.

Earlier we reported the presence of significant levels of antigalactocerebroside (GalC) antibodies in the sera of leprosy patients. This study corroborates the above result and also gives evidence for the presence of antibodies to the nonpolar ceramide (Cer) moiety of GalC. AntiCer antibody titres were higher as compared to antiGalC antibodies in all categories of leprosy. The specificity of antibodies directed to the Cer moiety was confirmed using Lactosyl-BSA and neutralization assays. Statistically significant and positive correlations were observed between antiGalC and antiCer antibodies. Responsiveness factors were computed using natural logarithmic transformation of the variables.

Immunoreactivity of nerve lipid antigens in leprosy.

Neural lipid antigens, namely, galactocerebroside and ganglioside, have been implicated in demyelinating diseases. We were interested in finding the role of these antigens in leprosy neuritis. The humoral immune response to these lipid antigens was quantitated by enzyme-linked immunosorbent assay in sera from 91 leprosy patients and 18 normal individuals. Our data revealed the presence of antibodies to total nerve lipids (TNL) and galactocerebroside (GalC) and a significantly low level to ganglioside (Gg) in all the categories of leprosy. No antilipid antibodies were detected in normals. Anti-TNL and anti-GalC antibodies were highest in tuberculoid leprosy patients. Statistically significant positive correlation was observed between anti-TNL and anti-GalC antibodies in lepromatous borderline, tuberculoid, and neuritic patients.

Macrophage membrane alterations in leprosy as determined by change in sialic acid level.

The level of sialic acid removable by neuraminidase from macrophages of bacteriologically-positive lepromatous leprosy (B(+)LL) patient is extremely low, compared to macrophages from tuberculoid leprosy patients or normal individuals. On the other hand macrophages from long term treated bacteriologically-negative lepromatous leprosy (B(-)LL) patients show a much higher level of sialic acid. This higher level is drastically reduced when these macrophages from (B(-)LL) patients are allowed to phagocytose Mycobacterium leprae. This modulation could be host- and pathogen-specific. It is demonstrated that M. leprae infection brings out membrane changes in the macrophages leading to alteration in the surface molecules. Such membrane changes may cause hindrance in the ability of macrophages to participate successfully in the immune process.