title: C1q enhances the phagocytosis of Cryptococcus neoformans blastospores by human monocytes.
abstract: We investigated whether C1q, a subunit of the first component of C, could modulate human peripheral blood monocyte-mediated phagocytosis of Cryptococcus neoformans (CN). Adherence of monocytes to C1q-coated surfaces induced a significant enhancement of ingestion of CN blastospores that had been opsonized with specific anticapsular IgG (IgG-CN). Additionally, C1q enhanced the monocyte-mediated phagocytosis of CN opsonized with C (CN-absorbed, nonimmune, normal human serum; C-CN). Ingestion of IgG- and C-CN by control and C1q-stimulated monocytes was maximal by 1 h of incubation. The monocyte-mediated enhancement of phagocytosis caused by C1q was paralleled by a proportionate increase in fungicidal activity, an effect which was maximal by 3 h of incubation. Human serum albumin-adherent, control monocytes exhibited only a low level of killing after 3 h of incubation. C1q enhancement was blocked by preincubation of the surfaces with a goat, polyclonal F(ab')2 anti-C1q. This study describes a new cellular function for the cell surface C1q receptor: the enhancement of phagocytosis of a pathogenic organism by monocytes.
authors.affiliation: Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
authors.forename: D A
authors.initials: DA
authors.lastname: Bobak
authors.forename: R G
authors.initials: RG
authors.lastname: Washburn
authors.forename: M M
authors.initials: MM
authors.lastname: Frank
mesh_terms: D000276:Adjuvants, Immunologic / Q000502:physiology; D000818:Animals; D001790:Blood Physiological Phenomena; D003166:Complement Activating Enzymes / Q000502:physiology*; D003172:Complement C1 / Q000502:physiology*; D015922:Complement C1q; D003454:Cryptococcus / Q000276:immunology*; D003455:Cryptococcus neoformans / Q000276:immunology*; D004340:Drug Contamination; D006801:Humans; D007074:Immunoglobulin G / Q000502:physiology; D009000:Monocytes / Q000276:immunology*; D009895:Opsonin Proteins; D010587:Phagocytosis / Q000187:drug effects*; D011817:Rabbits; D013172:Spores, Fungal / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D003172:Complement C1; D007074:Immunoglobulin G; D009895:Opsonin Proteins; D015922:Complement C1q; D003166:Complement Activating Enzymes