The Effects of Antigens and of Phytohemagglutinin on Rabbit Spleen Cell Suspensions

Abstract

Phytohemagglutinin (PHA) stimulated the rate of DNA synthesis in rabbit spleen cell suspensions. Unlike antigens, previous immunization to PHA was not necessary and the specific response could not be transferred by macrophages, although lymphocytes primed by incubation in PHA were able to stimulate other spleen cells not directly exposed to PHA. When rabbits were stimulated by in vivo immunization with antigens, spleen cells proliferating in response to antigen were stimulated to divide by in vitro contact with PHA. Using the technique of specific hemolytic plaque formation by individual cells synthesizing γM-antibody to sheep red cells (plaque-forming cells), no evidence was obtained that stimulation of cell division by PHA resulted in specific antibody formation, although the presence of antigen resulted both in stimulation of cell proliferation and the production of plaque-forming cells. The presence of both sheep red cells and PHA in the medium of the same cell suspensions did not enhance the production of plaque-forming cells although there was a summative effect on DNA synthesis.

A Specific Anamnestic Immune Response Induced by Plant Mitogens

“…Our results can also be reconciled with those of G engozian and H ubner [7], H arris and Littleton [10], and G reaves and F lad [8] who could not find unequivocal evidence that PHA or PWM induced a nonspecific anamnestic response. This is because the weak responses that we obtained could only be demonstrated when the background titres were very low, as they were with the cell transfer technique.…”

“…Some workers found that cells from sensitized animals produced increased amounts of specific antibody when treated with mitogens [21,6]. In other experiments the response was absent or equivocal [7,8,10].…”

Studies on Rabbit Peripheral Lymphocytes

“…[18] on the effect of antigen in vitro on rabbit spleen cells, a high rate of thymidine incorporation was demonstrated for the first 16 h of incubation followed by a sharp decrease during the second day. Similar results were obtained in this study.…”

Cells Involved in the Immune Response

“…The simultaneous addition of PHA and sheep red blood cells to cultures of lymphocytes obtained from rabbits previously immunized with sheep red cells induced a blastogenic response greater than that obtained with either PHA or antigen alone (18,19).…”