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HLA-DRB1*, -DQB1* in Piramalai Kallars and Yadhavas, two Dravidian-speaking castes of Tamil Nadu, South India

Authors

  • S. Shanmugalakshmi,

    1. Department of Immunology, Centre for Advanced Studies in Functional Genomics, School of Biological Sciences, Madurai Kamaraj University, Madurai, India
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  • K. Balakrishnan,

    1. Department of Immunology, Centre for Advanced Studies in Functional Genomics, School of Biological Sciences, Madurai Kamaraj University, Madurai, India
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  • K. Manoharan,

    1. Department of Immunology, Centre for Advanced Studies in Functional Genomics, School of Biological Sciences, Madurai Kamaraj University, Madurai, India
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  • R.M. Pitchappan

    Corresponding author
    1. Department of Immunology, Centre for Advanced Studies in Functional Genomics, School of Biological Sciences, Madurai Kamaraj University, Madurai, India
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Correspondence to:
Dr R. M. Pitchappan
Centre for Advanced Studies in Functional Genomics
School of Biological Sciences
Madurai Kamaraj University
Madurai 625 021
India
Tel: +91 452 2458269
Fax: +91 452 2459181 or 459139
e-mail: pitchappanrm@yahoo.co.uk

Abstract

Abstract:  Two Dravidian-speaking castes of Tamil Nadu, Piramalai Kallars (PKs, n = 205) and Yadhavas (YDs, n = 239) and a random panel (84) were studied for HLA-DRB1* and -DQB1* polymorphisms by DNA-SSOP typing methods. XI and XII International Histocompatibility primers and non-radioactive-labelled oligo probes were employed to identify the alleles. Results revealed that PKs possessed >0.1 allele frequencies of HLA-DRB1*15011, 0301, -DQB1*0201, 0501 and 0601; YDs, HLA-DRB1*0301, 0401, 07 and -DQB1*0601; and the random panel, DRB1*15021, 0401, 07, -DQB1 0201, 0301, 0302 and 0501. The highest frequency of DRB1*1501 in the world (GF = 0.225) was found in PKs. The most frequent two-locus haplotype (>500/10,000) in all the study samples was DRB1*10-DQB1*0501, while 1501–0601 was frequent in PKs and YDs. Comparison of the HLA-DRB1* data with Eastern European and South-East Asian populations suggested migration as the prime cause of the observed diversity in DRB1* allele frequencies. Nonetheless, the heterozygocity test and Watterson's homozygosity test indicated that balancing selection still operates on HLA-DRB1* locus, in this endemic region of various infectious diseases. This and spatial autocorrelation analysis support the view that selection may be a cause of ‘generating’ new variants and allelic diversity in different ancient settlements. The study suggested that South Indian, inbred, endogamous, sympatrically isolated castes or similar well-defined breeding isolates around the world, living under the same milieu-epidemiology, may be ideal models to test the immunogenetic basis of disease susceptibility.

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