Figure 1.

Reduced CD3ζ-chain expression in peripheral PBMCs from patients with tuberculosis. Freshly isolated PBMCs of five healthy donors and five patients with tuberculosis were adjusted to 2 × 10⁶ CD3ε positive staining cells as determined by flow cytometry before Western blot analysis. Detection of individual T-cell signalling molecules was performed with specific mAbs as described in the material and methods section. (a) Results obtained from PBMC of five different age-matched healthy donors (lanes 1–5); (b) results of five different tuberculosis patients (lanes 1–5). The expression level of ZAP-70, p56^lck and p59^fyn appeared to be similar in both groups. In contrast, CD3ζ protein expression was significantly reduced in patients with tuberculosis. The additional band in p56^lck or p59^fyn was observed in some samples obtained from patients with tuberculosis. The nature of this double band has not yet been defined, it may be associated with the activation status of peripheral T cells from patients with tuberculosis: Upon activation, lck or fyn are enriched in membrane lipid rafts, phosphorylate TCR invariant chains and associate with ZAP-70. These different configurations of lck or fyn (e.g. non-associated or associated with ZAP-70) may provide a reason for a different behaviour in SDS–PAGE analysis and also in Western blot.