Differential effect of isolated placental isoferritins on in vitro T-lymphocyte function

The effect of isoferritins isolated from human term placenta on certain T-lymphocyte parameters was studied in vitro using normal human lymphocytes. These isoferritins differed in ion exchange affinity, isoelectric point, and subunit composition. Only the acidic isoferritins caused a marked suppression of phytohaemagglutinin (PHA) blastogenesis and the most acidic isoferritin ('Acid I') was suppressive at a concentration as low as 0.25 microgram/ml. All four isoferritins suppressed concanavalin A (Con A) blastogenesis in a similar concentration dependent manner, with maximum effect at an isoferritin concentration of 1 microgram/ml. Both basic and acidic isoferritins reduced the Con-A-capping phenomenon in normal lymphocytes at concentrations higher than 0.5 microgram/ml, but at 0.25 microgram/ml only the acidic isoferritin was effective. The above findings support our previous report concerning the suppressive effect of splenic ferritin on T-lymphocyte function in vitro and indicate that acidic isoferritins, which often predominate in malignancy, demonstrate a higher degree of immunosuppressive activity. Thus, acidic isoferritins may play a role in the development of abnormal lymphocyte function encountered in certain proliferative disorders.