Immune Surveillance of Lymphoid Tissue. A Biological Role for the Mixed Lymphocyte Reaction

Abstract

Lymphocytes are readily activated by foreign lymphocytes both in vitro and in vivo under conditions in which they are not activated by most foreign tissue cells. Lymphocytes are also especially sensitive to the presence of abnormal proliferating lymphocytes even when they are autochthonous to the lymphocyte donor but they are little affected by many other tumour cells. It is proposed that mixed cell reactions, exemplified by the normal MLR, are distinct from normal homograft sensitisation mechanisms and that they represent a surveillance mechanism which is especially effective in the removal of aberrant lymphoid cells.