human leucocytic antigen (hla) typing in patients with allergic rhinitis

Allergic rhinitis is u hercdofuruiliul disease with Ull atopicpredisposition. it is mostly found in association with exposure toaeroallergens.· A similar syndrome is occasionally observed in aminority of susceptible individual following ingestion of foods, butimmunological basis for these reactions is an yet to be established.Allergic rhinitis is either seasonal or perennial. Perennial rhinitis withsever exacerbation is common. Studying the genetic markers amongallergic patients to confirm the hereditary tendency was a must.However, the most important genetic marker is HLA system whichhas extreme polymorphism and is subjected to marked geographicaland racial variations.The human leucocyte antigens (Hl.A) system is cluster of geneslocated on the short arm of the chromosome number 6 . It consists ofthree regions, class I, II and III. The class 1 genes (1ILA-A,-B. and -C)encode cell surface antigens that are expressed on most nucleated cell,whereas the class II genes (lILA-OP, -OQ and -OR) encode surfaceantigens which are expressed only by few number of cells;monocytes, rnacrophages, B-Iymphocytes and activated T-lymphocytes. The class III genes encode complement components(C2 and C4), properdin factor B (BF) and tumour necrosis factors aand p.The various mechanisms involved in the regulation of theImmune response of the body are under the control of HLA system.