Monocyte-platelet interaction in immune and nonimmune thrombocytopenia.
Platelets from 24 patients with immune thrombocytopenia resistant to standard therapy (refractory ITP), 35 patients with nonimmune thrombocytopenia (non-ITP), and 32 normal donors were studied in regard to platelet surface-bound IgG (PBIgG) and the ability of these platelets to be bound by human monocytes in vitro (monocyte-platelet rosette assay). Fourteen (58%) of the platelet samples from refractory ITP patients but none (0%) from the non-ITP or control donors had PBIgG greater than 800 molecules IgG/platelet. Seventeen of 24 (71%) of the ITP patients had platelets which demonstrated increased monocyte-platelet rosette formation [rosette index (RI) greater than 2], whereas only four (11%) of the non-ITP patients had such platelets. There was a direct correlation between PBIgG and rosette index for the platelets from resistant ITP patients. There was no correlation of severity of thrombocytopenia with PBIgG or rosette index. Monocyte-platelet interaction in the presence of elevated PBIgG is mediated through the monocyte Fc-receptor. Platelets from five of ten refractory ITP patients with PBIgG less than 800 molecules IgG/platelet had increased rosette formation. Monocyte-platelet interaction in the absence of increased PBIgG may be due to small amounts of platelet surface IgG which are still able to mediate monocyte Fc-receptor interaction or to alternate membrane receptor interaction through the monocyte C3 receptor. Our data underscore the pathophysiologic relevance of monocyte/macrophage-mediated interaction in immune platelet destruction syndromes.
Saleh
M N
MN
Division of Hematology/Oncology, University of Alabama, Birmingham 35294.
Moore
D L
DL
Lee
J Y
JY
LoBuglio
A F
AF
D001323:Autoantibodies / Q000032:analysis; D001666:Binding Sites, Antibody; D001792:Blood Platelets / Q000502:physiology*; D002450:Cell Communication; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D009000:Monocytes / Q000502:physiology*; D010976:Platelet Count; D011696:Purpura, Thrombocytopenic / Q000097:blood / Q000276:immunology / Q000473:pathology*; D012397:Rosette Formation; D013921:Thrombocytopenia / Q000097:blood / Q000473:pathology*
D001323:Autoantibodies; D007074:Immunoglobulin G