Dominating defects in SLE are demonstrated in humoral immune response, however, various T cell defects were observed. Recently, some authors referred to about the abnormalities in signalling after TCR activation and about CD3ζ chain deficiency of some SLE patients (1,2,3). The reports differed in many details and, therefore, we decided systematically to test these results and to study molecular architecture of such signalling complex.

Isolated periferal blood lymphocytes (PBL) from SLE patients and controls were analyzed for the presence of CD3ζ chain using immunoblot assay with mouse monoclonal anti-CD3ζ chain antibody and secondary antibody conjugated with peroxidase followed by chemiluminiscence. Lysis of PBL was performed either following the method of American authors (1,2) or by the method used in the laboratories studying the molecular aspects of TCR signalization (e.g. Dr. V. Hoøejší, Prague). T cell signallization was stimulated by cross-linking TCR with monoclonal antibody against CD3ζ (MEM-92) and tyrosine phosphorylated proteins were detected using monoclonal antibodies (P-TYR1 and P-TYR2) by immunoblotting.

The defect of CD3ζ chain was found in 17 of 45 SLE patients (38 %) using the protocols published by American group and was never found in 15 controls (healthy or not SLE patients). But, we could not find this defect using the improved protocol in 59 SLE patients, including all of the previous group. Signalling was different in patients compared to controls in that unstimulated cells from patients showed the pattern observed in stimulated controls but the results were dependent on the conditions by which PBL were brought to the so-called "inactive" or quiet state.

Conflicting results show that the published CD3ζ chain deficiency in SLE patients could be caused by the methodical approach. Defect in signalization must be defined more precisely under strictly controlled conditions.