title: Opsonization requirements of Serratia marcescens.
abstract: Dextran-separated human peripheral blood leukocytes (55 vol%) from healthy adults served to delineate the opsonic requirements of various serologically defined assay strains of Serratia marcescens. 'Natural' antibodies of three commercial IgG immunoglobulin preparations (25 vol%), in the absence of complement (C), did not opsonize all 19 test strains, in particular certain strains carrying O-antigens O6 and/or O14, despite documented (ELISA technique) contents of anti-O6 and -O14 IgG antibodies. The 'natural' IgG opsonins proved O-antigen specific. Several of 13 selected assay strains of S. marcescens differed in opsonic requirements for 'classically' or 'alternatively' activated human C; opsonization was optimal with intact fresh human serum (25 vol%). All 13 tested strains activated both pathways of C. Anti-live cell rabbit immune sera (RIS) surpassed conventional anti-O and anti-H RIS (25 vol%) in terms of opsonizing activity, which proved partially heat-labile and O-antigen specific for two, but not for two other test strains. Isolated IgM immunoglobulin fractions of anti-live cell RIS either totally lacked or displayed inferior opsonizing activity in the absence of C, although O-agglutinin activity was only from 4- to 8-fold lower than that of unfractionated anti-live cell RIS. Human and rabbit 'natural' IgM antibodies opsonized moderately. Added guinea pig C (10 vol%) failed to enhance opsonizing activity of 'natural' and 'immune' rabbit IgM and 'natural' human IgG and IgM antibodies.
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology; D003167:Complement Activation; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D019081:O Antigens; D009895:Opsonin Proteins / Q000276:immunology*; D011817:Rabbits; D012706:Serratia marcescens / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D019081:O Antigens; D009895:Opsonin Proteins