Stimulating activity of Brucella fractions in a human lymphocyte transformation test. Correlation with humoral and cellular immunity.

'PI' a phenol-extracted fraction from Brucella melitensis has been used for years in our laboratory for the vaccination of laboratory and agricultural workers considered 'at risk'. In the present work it has been used in vitro, together with another phenol-extracted and peptidoglycan containing fraction (4A) in a lymphocyte transformation test. Correlation between stimulation index, humoral antibodies to Brucella and the cutaneous response to PI have been studied in subjects vaccinated with the PI fraction, in Brucellosis patients and normal controls.