Anti-microbial antibodies have been found useful for diagnosis of Crohn’s disease (CD) and Sjogren’s syndrome (Sjo). These antibodies are also elevated in other autoimmune disease such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and multiple sclerosis (MS). The prevalence of these antibodies in the normal healthy population is unknown. We set to survey the normal population for these anti-microbial antibodies in comparison with Crohn’s disease and others. Totally 288 blood samples from the donor units of the leukocyte-reduced red blood cells from the American Red Cross were examined for the presence of anti-microbial antibodies using direct ELISA assays established in our laboratory using the recombinant microbial protein antigens.