Human platelets can initiate T cell-dependent contact sensitivity through local serotonin release mediated by IgE antibodies.
To investigate the role of human platelets in initiating Ag-specific contact sensitivity (CS), a mouse model employing human platelets was used. Intravenous injection of immune lymphoid cells containing Ag-specific CS-effector Thy1+ B220- T cells that were depleted of CS-initiating Thy1+, B220+ cells together with human platelets presensitized in vitro with Ag-specific IgE mAb led to elicitation of CS responses in recipient mice. The fact that this response was blocked by preincubation of platelets with an irrelevant IgE or with a mixture of anti-Fc epsilonRI alpha mAb and anti-Fc epsilonRII mAb suggested that IgE Fc epsilonR on platelets were involved. When platelets that were presensitized with Ag-specific IgE mAb were incubated in vitro with specific Ag in the presence of fresh mouse serum, a significant net release of [3H]serotonin (5-hydroxytryptamine, 5-HT) was observed. Furthermore, in vitro depletion of 5-HT from platelets or in vivo pretreatment of recipients with a 5-HT2A receptor antagonist (ketanserin) abolished the IgE-dependent CS initiation mediated by platelets. These results show that human platelets can initiate T cell-dependent CS responses through IgE mAb, and this CS initiation is mediated by 5-HT released from the platelets in an Ag-specific manner.
Matsuda
H
H
Department of Veterinary Clinic, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Japan.
Ushio
H
H
Geba
G P
GP
Askenase
P W
PW
D000818:Animals; D001792:Blood Platelets / Q000276:immunology* / Q000378:metabolism / Q000502:physiology*; D002450:Cell Communication / Q000276:immunology*; D003165:Complement System Proteins / Q000502:physiology; D003877:Dermatitis, Contact / Q000097:blood* / Q000209:etiology* / Q000276:immunology; D007073:Immunoglobulin E / Q000097:blood / Q000502:physiology*; D008297:Male; D008407:Mast Cells; D051379:Mice; D008805:Mice, Inbred A; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D008817:Mice, Mutant Strains; D044402:Receptor, Serotonin, 5-HT2A; D017455:Receptors, IgE / Q000097:blood / Q000502:physiology; D011985:Receptors, Serotonin / Q000378:metabolism; D012701:Serotonin / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology*
D044402:Receptor, Serotonin, 5-HT2A; D017455:Receptors, IgE; D011985:Receptors, Serotonin; D012701:Serotonin; D007073:Immunoglobulin E; D003165:Complement System Proteins