Biochemical studies on cells involved in immune responses

Research over the last decade has indicated a possible role in the immune response for RNA extracted from peritoneal exudate cells after exposure to antigen for short time intervals in vitro. The synthesis of RNA was studied in antigen stimulated peritoneal exudate cells. Studies were also carried out on the capacity of a particulate antigen (T2 phage) and a soluble antigen (BSA) to combine with RNA. The effect of antigen on the rate of uptake of precursors into protein, DNA and lipid was also investigated and an attempt made to correlate these changes with changes found in RNA metabolism. The results obtained showed that the uptake of (3H) uridine and (14C) leucine into acid-precipitable material of rabbit peritoneal exudate cells was increased in the presence of T2 phage. The increase was found to be proportional to the amount of T2 phage added. At the same time incorporation of (14C) thymidine and 32-phosphate into DNA and phospholipid of peritoneal exudate cells was decreased in the presence of phage. This decrease bore an inverse relationship to the amount of T2 phage added. Sucrose gradients were used to evaluate the character of RNA species synthesised by peritoneal cells in the presence of the antingen and it was found that most of the (3H) uridine had been incorporated into ribosomal and preribosomal species. When antigen was added to a similar culture, over the same 30 minute period, there was no increase in labelling of low molecular weight RNA as described by others, but rather there was (if anything) a small increase in labelling of ribosomal and pre-ribosomal RNA. These results could be interpreted along with the increased leucine uptake into protein in presence of antigen to indicate increased ribosomal protein and RNA synthesis directed towards increased production of lysosomal enzymes. The depression of the uptake of thymidine and phosphate by antigen suggests an antigen induced inhibition of cell division on the part of cells reorganising themselves to degrade the ingested antigen. A second system involving possible co-operation between cell types was selected for study. Many authors had noted that the appendix exhibited a very high rate of DNA synthesis yet this tissue has not yet been shown to produce antibody. Suggestions have been made that cells from the appendix migrate to the spleen where they become producers of IGM antibody. A comparison was made between thymidine uptake bye appendix cells from immunised rabbits in the presence and absence of the immunising antigen. Thymidine uptake into appendix cells was found to be slightly increased in the presence of antigen. However, when bovine serum albumin was used as the immunising antigen, subsequent incubation of the appendix cells with bovine serum albumin led to inhibition of thymidine uptake in 1 of 10 animals investigated. On the other hand if bovine gamma globulin was used as the immunising antigen then secondary re-encounter of appendix cells with this antigen in vitro would lead to inhibition of thymidine uptake on 3 out of 5 occasions. Studies were carried out on mixed suspensions of spleen and appendix cells cultured in the presence of antigen. In this case, uptake was higher than would have been predicted on the basis of uptake by each cell type separately