Antigen specific lymphocyte activity in vitro by peripheral blood leucocytes from Mantoux positive and negative human beings. I. Comparison of quantitative and qualitative differences in the PPD-specific lymphoproliferative response of lymphocytes from the two kinds of donors.

Lymphocytes from some PPD (purified protein derivative from tubercle bacillus) skin test negative (Mantoux negative=Mx--) human beings reacted against PPD in the lymphoproliferative assay with a time course and dose response very similar to those of lymphocytes from Mantoux positive (Mx+) individuals. Other Mx-- persons were PPD non-responsive in the lymphoproliferative assay. The PPD response of (immunoglobulin=Ig) Ig anti-Ig column passed lymphocytes (T-cells) from Mx--/LP+ (LP+=lymphoproliferative) persons was significantly reduced whereas the in vitro PPD response of T-lymphocytes from Mx+/LP+ was the same or increased. Purified B-lymphocytes from all kinds of tested individuals did not respond in vitro against PPD. Serological investigations indicated that one of the reasons for the negative skin reaction of individuals whose lymphocytes gave a positive lymphoproliferative response against PPD in vitro, is that such individuals had recirculating PPD of high molecular weight (greater than 900,000) and/or PPD anti-PPD antibody complexes in the serum. These substances could block the PPD-specific T-lymphocytes.