Structure and biological functions of human IgD. XII. Anti-IgD enhancement of PHA responsiveness in patients with chronic lymphocytic leukaemia.

Specifically purifed anti-human delta stimulated the in vitro incorporation of [3H]thymidine by human peripheral lymphocytes from patients with chronic lymphocytic leukaemia (CLL). The peak response varied between individuals; those with 5--52% IgD-bearing lymphocytes exhibited maximum stimulation at 3 days, whereas a patient with only 1% IgD-bearing cells showed optimal activation at 6 days. In agreement with others, our data indicated that, in most instances, lymphocytes from patients with CLL respond poorly to PHA. One of the most important findings in this study is the enhancement of PHA responsiveness by anti-delta. Lymphocytes that exhibited reduced responsiveness to PHA alone, when pre-treated with anti-delta, showed transformation greater than the sum of the anti-delta plus PHA responses.