The inhibition of polymorphonuclear and lymphocyte-mediated fetal red blood cell lysis by promethazine in vitro

Abstract

An in vitro method for the measurement of fetal red blood cell destruction by Fc receptor-bearing polymorphonuclear leukocytes and lymphocytes has been developed. Cord blood was collected at the time of delivery from infants who were Rh-D positive and compatible with their mother, as well as infants who were Rh-D positive and incompatible with their Rh-D-sensitized mothers. Red blood cells, lymphocytes, and polymorphonuclear preparations were individually separated from each cord blood sample. Rh-D-positive cord red blood cells from compatible and incompatible pregnancies complicated by erythroblastosis were coated with anti-Rh-D. All target red blood cells, opsonized and not opsonized, were labeled with chromium-51 and cultured with autologous lymphocytes or polymorphonuclear leukocytes at an effector:red blood cell ratio of 10:1. Cultures containing either no promethazine hydrochloride or varying amounts of the drug were studied. Antibody alone did not cause red cell lysis. Both lymphocytes and polymorphonuclear leukocytes were effective in causing the lysis of red blood cells bearing antibody. Lysis of red blood cells by polymorphonuclear leukocytes or lymphocytes was inhibited by promethazine hydrochloride. Excessive amounts of promethazine hydrochloride alone cause lysis of the red cells. At the low doses utilized for inhibition in this experiment, the action of promethazine hydrochloride on the lymphocytes was found to be reversible. Promethazine is believed to have exhibited two different types of activity in this study: (1) It inhibited antibody-dependent, cell-mediated lysis of autologous red blood cells coated with antibody; (2) it stabilized the red blood cell membrane so that even spontaneous lysis of red blood cells was decreased 50 per cent.