Immunogenetics of mixed connective tissue disease in a Mexican Mestizo population

A.L. Weckmann, J. Granados, M.H. Cardiel, F. Andrade, G. Vargas-Alarc&oacuten, J. Alcocer-Varela, D. Alarc&oacuten-Segovia

Department of Immunology and Rheumatology, Instituto Nacional de la Nutricion Salvador Zubiran, Tlalpan, Mexico City, Mexico.


ABSTRACT
Objective
The aim of this study was to determine the HLA antigens in Mexican Mestizo patients with mixed connective tissue disease (MCTD).

Methods
We studied 30 patients with MCTD and 99 healthy controls. HLA-A, -B, and -DQ antigens were typed by microlymphocytotoxicity assays. DRB1, DQA1 and DQB1 alleles were oligotyped.

Results
HLA-A2 and HLA-B35 were the most frequent MHC class I alleles in MCTD patients, although they were not statistically more frequent than in the controls. According to serological tests, the most frequent DQ allele in the patients was DQ1, which was statistically increased when compared with controls (p = 0.0051). By oligotyping, the DR1 allele and the DQB1* 0501 specificities were significantly increased in the patients vs. controls (p = 0.032 and 0.027, respectively).

Conclusion
The elevated levels of DQ1 found in Mexican MCTD patients, although weak, may indicate a particular genetic susceptibility, since there are previous reports of associations of other alleles (such as DR4) with MCTD in other populations. The increase in DQB1* 0501 may account for the increase in DQ1. DQB1*0501 has also been reported in black patients with anti-RNP autoantibodies, compared with black patients without anti-RNP or anti-Sm.

Key words
Connective tissue diseases, HLA, immunogenetics, autoimmunity.

Ana Luisa Weckmann, MSc, Research Fellow; Julio Granados, MD, Staff Researcher; Mario H. Cardiel, MD, Staff Researcher, Rheumatologist and Clinical Epidemiologist, recipient of the Gustavo Baz Prada nominal chair; Felipe Andrade, MD, Research Fellow; Gilberto Vargas-Alarcon, PhD, Research Fellow; Jorge Alcocer-Varela, MD, Professor and Chairman of the Dept. of Immunology and Rheumatology; Donato Alarcon-Segovia, MD, General Director of the Instituto Nacional de la Nutricion Zubiran.

This work was supported in part by the grant Nr. 3653-M9311 from the Consejo Nacional de Ciencia y TecnologÌa (CONACYT), Mexico.

Please address correspondence and reprint requests to: Dr. Julio Granados, Department of Immunology and Rheumatology, Instituto Nacional de la Nutricion Salvador Zubir·n, Vasco de Quiroga No. 15, Tlalpan, CP 14000, Mexico City, Mexico.

Received on March 4, 1998; accepted in revised form on August 28, 1998.

Clin Exp Rheumatol 1999; 17: 91-94.
© Copyright Clinical and Experimental Rheumatology 1999.