Abstract: New and improved methodology for the diagnosis of a disease from blood sample analysis is disclosed and comprises: the preparation of a putative antigenic body substance extract, which is specific to disease-sensitized blood leukocytes, from the pooled, like body substances of a plurality of donors known to have the disease of interest; the mixture of said extract with the blood sample leukocytes; the promotion of the reaction therebetween to modify a characteristic of the disease-sensitized leukocytes, if any, of the blood sample; and the determination of the extent, if any, to which said characteristic has been modified. In multiple sclerosis diagnosis, said body substance may be blood or urine; while for malignant disease (for example breast cancer, or cancer of the head and neck) said body substance may be blood, urine, pleural fluid, ascites fluid, supernates of tumor cells or tumor cells grown in culture media.