Immunological studies in typhoid fever. I. Immunoglobulins, C3, antibodies, rheumatoid factor and circulating immune complexes in patients with typhoid fever.

The development of O, H and Vi antibodies to Salmonella typhi antigens, immunoglobulins and C3 levels, and the presence of rheumatoid factor and circulating immune complexes were determined in the sera of patients with typhoid fever and appropriate age and sex-matched controls. IgM, and both O and H antibodies were raised in typhoid patients. Rheumatoid factor, a possible indicator of persistent circulating immune complexes, was also present in these patients. Immune complexes were more often present in patients with typhoid fever than in controls, their presence was much more marked in complicated cases of typhoid fever. A high ratio of alpha 1-antitrypsin to C3 was found in these patients suggesting complement consumption.