Ans. is 'a' i.e., ds DNA Antinuclear antibodies in SLEo Systemic lupus erythematosus is characterized by bewildering array of autoantibodies, particularly antinuclear antibodies.o The antibodies are directed against an array of nuclear and cytoplasmic components of the cell, in addition a third group of antibodies is directed against cell surface antigen of group cells,o The existence of seemingly limitless number of antibodies in patients against self-constituents indicate that the fundamental defect in SLE is a failure of the mechanism that maintain self-tolerance.o ANA is positive in virtually every patient of SLE, hence this test is sensitive but is not specific because patients with other autoimmune diseases are also positive.o Of the numerous antinuclear antibodies, antibodies to double stranded DNA and the antibodies, to (Smith) antigen are virtually diagnosis of SLEQ.o Presence of abtibodies to antismith and anti double stran ded DNA is virtually diagnostic of SLE.o The best serening test for SLE is demonstration of antinuclear antibodies.o Most sensitive antibody test for SLE - Antinuclear antibody test for SLE.o Afost specific antibody test for SLE - Anti ds DNA and Anti Sm antibodyo Antibody associated with drug induced SLE - Antihistone antibodyAutoantibodies in Systemic Lupus Ery thematosus (SLE! Prevalence Antibody%Antigen RecognizedClinical Utilityo Antinuclear antibodies98Multiple nuclearBest screening test; repeated negative tests make SLE unlikelyo Anti-ds DNA70DNA (double-stranded)High titers are SLE-specific and in some patients correlate with disease activity, nephritis, vasculitiso Anti-Sm25Protein complexed to 6 species of nuclear U1 RNASpecific for SLE; no definite clinical correlations; most patients also have anti-RNP; more common in blacks and Asians than whiteso Anti-RNP40Protein complexed to U1 RNAyNot specific for SLE; high titers associated with syndromes that have overlap features of several rheumatic syndromes including SLE; more common in blacks than whiteso Anti-Ro (SS-A)30Protein complexed to hY RNA, primarily 60 kDa and 52 kDaNot specific for SLE; associated with sicca syndrome, predisposes to subacute cutaneous lupus, and to neonatal lupus with congenital heart block; associated with decreased risk for nephritis -o Anti-La (S3-B)1047-kDa protein com- plexed to hY RNAUsually associated with anti-Ro; associated with decreased risk for nephritiso Antihistone70Histones associated with DNA (in nucleo-some, chromatin)More frequent in durg-induced lupus than in SLEo Antiphospholipid50Phospholipids, b2 glycoprotein 1 cofac- tor prothrombinThree tests available - ELISAs for cardiolipin and b2G1, sensitive prothrombin time (DRVVT); predisposes to clotting, fetal loss, thrombocytopeniao Antierythrocyte60Erythrocyte membraneMeasured as direct Coombs' test; a small proportion develops overt hemolysiso Antiplatelet30Surface and altered cytoplasmic antigens on plateletsAssociated with thrombocytopenia but sensitivity and specificity are not good; this is not a useful clinical testo Anti neuronal (includes anti-glutamate receptor!60Neuronal and IvmphoIn some series a positive test in CSF correlates with cyte surface antigens active CNS lupuso Antiribosomal P20Protein in ribosomesIn some series a positive test in serum correlates with depression or psychosis due to CNS lupus