Inhibition of 3H-thymidine incorporation into human lymphocytes by dialyzable material of streptokinase- streptodornase.

Using the 3H-thymidine incorporation test, the lymphocyte-stimulating activity of streptokinase-streptodornase (SK-SD, Varidase) and its fractions were evaluated. The dose-response curves of all the preparations except the third fraction had two peaks with the maximum around 5 and 40 mug. The dialyzable fraction of Sk-SD (D-SK-SD) occupying approximately half of the original sample had almost no lymphocyte-stimulating activity; and conversely, it had a potent inhibitory effect on the 3H-thymidine incorporation into lymphocytes that normally occurs with non-dialyzable SK-SD (ND-SK-SD), PPD and PHA-P. Therefore, it will be desirable to remove the dialyzable fraction from the commercial SK-SD preparation when it is used for the determination of the capacity of cellular immunity against tsk-sd.