Changes in expression of signal transduction proteins in T lymphocytes of patients with leprosy

Abstract

Advanced stages of mycobacterial diseases such as leprosy and tuberculosis are characterized by a loss of T-cell function. The basis of this T-cell dysfunction is not well understood. The present report demonstrates major alterations in the expression of signal transduction molecules in T cells of leprosy patients. These alterations were most frequently observed in lepromatous leprosy (LL) patients. Of 29 LL patients, 69% had decreased T-cell receptor zeta-chain expression, 48% had decreased p56(lck) tyrosine kinase, and 63% had a loss of nuclear transcription factor NF-kappaB p65. An electrophoretic mobility shift assay with the gamma interferon core promoter region revealed a loss of the Th1 DNA-binding pattern in LL patients. In contrast, tuberculoid leprosy patients had only minor signal transduction alterations. These novel findings might improve our understanding of the T-cell dysfunction observed in leprosy and other infectious diseases and consequently might lead to better immunologic evaluation of patients.

FIG. 1

Reduced expression of TCRζ and p56^lck in LL patients. Representative Western blots of TCRζ and CD3-ɛ (A to C) and p56^lck tyrosine kinase (D to F). HT, B-cell line used as a negative control; N, normal human T cells. Numbers on the left are molecular masses in kilodaltons.

FIG. 2

Densitometry values for the ζ-chain from Fig. 1A to C are presented in panels A to C, respectively. TCRζ expression levels that were ≤55% of the mean levels for the normal controls on each gel were considered to be decreased (see Materials and Methods). O.D., optical density.

FIG. 3

Decreased expression of nuclear NF-κB and absence of Th1 DNA-binding pattern in LL patients. (A) Western blotting for NF-κB and c-Rel, p65, and p50 was done with nuclear extracts from purified T cells taken from normal (healthy) controls (N) and tuberculoid (T) and lepromatous (L) patients and previously activated for 2 h with 1 μg of anti-CD3 per ml. Numbers on the left are molecular masses in kilodaltons. (B) EMSA for Th1 with an IFN-γ core promoter region. The four bands shown by the arrows are consistently seen in cells from healthy controls and Th1 cells.

FIG. 4

Predominant Th2 cytokine patterns in LL patients. Levels of cytokine production (IFN-γ, IL-1β, IL-10, and IL-6) in normal (healthy) controls (N) and TL and LL patients were determined after stimulation of PBL-T with soluble anti-CD3 for 48 h.