title: Detection of functional platelet-activating factor receptors on human tonsillar B lymphocytes.
abstract: Although platelet-activating factor (PAF) receptors have been found on B lymphoblastoid cell lines, the action of PAF on freshly isolated human B cells has not been clearly demonstrated. Using a sensitive semiquantitative reverse-transcriptase PCR, we have found PAF receptor mRNA expressed by tonsillar B lymphocytes, but little in T lymphocytes. Examination of Percoll-fractionated tonsillar B cells indicated that the low density (primarily germinal center cells) and medium density fractions had approximately twofold more PAF receptor mRNA relative to the high density fraction. PAF (10-7 M) stimulated increases in intracellular Ca2+ that were consistently higher in the low and medium density B lymphocytes compared with high density cells. The PAF receptor antagonist Web 2170 inhibited this. Addition of PAF, but not lyso- or enantio-PAF, induced four- to sixfold greater synthesis of IgM and IgG in low and medium density cells compared with unstimulated controls, but had little effect on Ig production by high density cells. To investigate how PAF may influence Ig synthesis, PAF-stimulated B cells were examined for production of the Th2-type cytokines IL-4 and IL-13. PAF induced IL-4 and IL-13 mRNA expression in 17% of CD20+ cells, and IL-4 was detected in cell supernatants after 48-72 h of culture. Together, these data strongly suggest that functional PAF receptors are expressed on B cells in tonsils.
authors.affiliation: Division of Allergy and Immunology, McGill University/Montreal Children's Hospital Research Institute, Quebec, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Bastien
authors.forename: B J
authors.initials: BJ
authors.lastname: Toledano
authors.forename: N
authors.initials: N
authors.lastname: Mehio
authors.forename: L
authors.initials: L
authors.lastname: Cameron
authors.forename: B
authors.initials: B
authors.lastname: Lamoukhaid
authors.forename: P
authors.initials: P
authors.lastname: Renzi
authors.forename: Q
authors.initials: Q
authors.lastname: Hamid
authors.forename: B D
authors.initials: BD
authors.lastname: Mazer
mesh_terms: D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002452:Cell Count; D002478:Cells, Cultured; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D018793:Interleukin-13 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000378:metabolism; D016131:Lymphocyte Subsets / Q000737:chemistry / Q000378:metabolism; D014066:Palatine Tonsil / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000378:metabolism* / Q000502:physiology; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D018793:Interleukin-13; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D015847:Interleukin-4; D002118:Calcium