1976 Volume 26 Issue 2Supplement Pages 135-142
In the previous manuscript, authors reported that PSPS consisted mostly of proteins with small amounts of hexoses and riboses ; that revealed and ability to induce feeble Shwartzman reactions in rabbits and to produce the homocytotropic antibody in rats with relatively high titers. In this paper, PSPS had another aspect of biological activity as an inhibitory effect upon the TdR incorporation into human leucocytes stimulated with PPD, streptococcal M-protein and SK-SD, respectively.
The results obtained were as follows :
1) PSPS was able to stimulate the human leucocytes of healthy subjects in 2 out of 7 persons in whom stumulation index (S. I.) revealed 3 and 13, respectively.
2) On the contrary, PSPS inhibited the TdR incorporation into leucocytes stimulated with PPD, streptococcal M-protein and SK-SD when that was given simultaneously with those antigens to a large extent of showing more than 70% of percentage inhibition in an individual case.
3) Of particularly curious thing was that in a case (donor T. K.) in which the PSPS obviously stimulated the leucocytes with an increased TdR in corporation, inversely that inhibited TdR incorporation with approximate 70% of percentage inhibitions when was given simultaneously with specific antigens.
4) There was a trend toward more increment of percentage inhibition in such a condition that the PSPS was given simultaneously or 2 hrs before the antigen stimulations with PPD, streptococcal M- protein and SK-SD in comparison with that 2hrs after antigen stimulations, suggesting a possible involvement of competitive binding between the receptors for antigens and for PSPS.
5) Trypan blue exclusion test was carried out in order to exclude the cytotoxic activity of PSPS upon the leucocytes with the resultant data of over 80% viable cells remaining at 3, 4 and 5 day cultures.
Thus, though PSPS was able to stimulate those leucocytes with the increased TdR incorporations in a part of healty subjects, that inversely inhibibited the TdR incorporations when was stimulated simulutaneously with the specific antigens. The mechanisms underlying these mutable contradictory actions of PSPS upon the human leucocytes should be more clarified on the basis of its chemical purification and mutual competitive inhibition of cell surface receptors involved in the regulation of DNA synthesis in nucleus.
