anti-apolipoprotein antibodies anti-apolipoprotein antibodies in autoimmune disease, anti-apolipoprotein h (aaha) antibodies, also called anti-β2 glycoprotein i antibodies, comprise a subset of anti-cardiolipin antibodies and lupus anticoagulant. these antibodies are involved in sclerosis and are strongly associated with thrombotic forms of lupus. as a result aaha are strongly implicated in autoimmune deep vein thrombosis. autoantibody anti-apolipoprotein,β-2 glycoprotein 1 autoantigenisoformapolipoprotein h autoantigen geneapoh affected organ(s)cardiovascular affectedtissue(s)serum affected cell(s)blood platelets also affectedserum proteins associateddisease(s)idiopathic thrombosis, sclerosis, systemic lupus erythematosus dr4-dq3 hla associationsdr53 drb1*0402 (dr4) also, it was proposed that aaha is responsible for lupus anticoagulant. however, antiphospholipid antibodies bind phospholipids at sites similar to sites bound by anti-coagulants such as pap1 sites and augment anti-coagulation activity. this contrasts with the major, specific, activity of aaha, defining a subset of anti-cardiolipin antibodies that specifically interacts with apo-h. ahaa only inhibits the anti-coagulation activity in the presence of apo-h and the aaha component of acla correlates with a history of frequent thrombosis. this can be contrasted with lupus anticoagulant which inhibits agglutination in the presence of thrombin. a subset of ahaa appear to mimic the activity of lupus anticoagulant and increase apo-h binding to phospholipids. these two activities can be differentiated by the binding to apo-h domains, whereas binding to the 5th domain promotes that anti-coagulant activity binding to the more n-terminal domains promotes lupus anticoagulant-like activities. aaha interferes with factor xa inhibition by apo-h increasing factor xa generation. however, like apo-h the lupus anticoagulant inhibits factor xa generation. aaha also inhibited the autoactivation of factor xii while at high aaha concentrations, factor xiia activation increases at levels comparable to apo-h that cause inhibition of factor xiia activation. a synchronized inhibition of factor xii autoactivation by apo-h and ahaa has been suggested. genetics the haplotype hla-dr4-dq3 appears to play a role in the pathogenic aaha production. the alleles primarily recognized are hla-dr53 (drb4*01), drb1*0402, dqa1*03, and possibly dqb1*0302. all of these alleles are in linkage disequilibrium in the drb4*01:drb1*0402:dqa1*0301:dqb1*0302 haplotype, also called dr4-dq8 and also the dqa1:0303:dqb1*0301 haplotype, dr4-dq7.3. however in european americans which reflects a broad area of europe in which the original studies were conducted only dr4(0402)-dq8 was found, indicating that the entire haplotype is involved. hla-dr7 may also be associated with these antibodies and the common haplotype association is the hla-dr53 serotype.