Seventy-four cases of clinically diagnosed Rheumatoid Arthritis (RA), fifty cases of systemic lupus erythematosus (SLE), and thirty healthy normal controls were investigated for detection of rheumatoid factor (RF), total serum immunoglobulins (Igs), antinuclear antibody (ANA), and ANA subtype anti-double stranded DNA (anti-ds DNA). Patients with RA showed 58.1% positive for RF comparable with 14% positivity in SLE patients and 6.6% in normal individuals. Serum Igs (IgA,IgG) were found to be

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... ated in RA and SLE patients (62.2% , 36.5%) (54% , 38%) respectively. This study revealed that ANA is found in 88% of SLE patients sera and 78% of these ANA is ds DNA in comparison with only 6.8% of RA sera were found positive for ANA. __________________________________________________________________________________________ Introduction:______________________________ RA is a chronic systemic inflammatory autoimmune disorders of mysterious aetiology, which is dominated by joint inflammation accompanied by several peripheral inflammatory manifestations . In this disease patients develop distinct immuno abnormalities espe-cially autoantibodies, among these antibodies is RF which is a major immunological abnormality in RA and regarded as one of the diagn-ostic criteria of RA which is included in the American College of it may occur even in some normal individuals (4). It is well accepted that anti-ds DNA antibodies are rather specific to SLE with occurance in 70% but detected in less than 5% in RA patients (5). RF, ANA and anti-ds DNA appear in RA as well as SLE patients sera. Patients and methods Study population : The study cohort comprised 74 sera samples for patients (19male and 55 female), their age range (18-67 years) with RA who met (ACR) 1987 reversed criteria (1) attending the Rheumatology Consultation Clinic or admitted to Baghdad Teaching Hospital in the period between November 2001 and February 2002.  Control group: were sex and age matched. They were included :-_________________________________________