Journal of ImmunologicalMethods, 47 (1981) 113--120 113 Elsevier/North-Holland Biomedical Press A SIMPLE AND RAPID LATEX FIXATION TEST FOR MEASURING IMMUNOGLOBULINS PRODUCED IN CELL CULTURES TADASHI KASAHARA, HIROTOMO HARADA I,HIROMITSU ENOMOTO I, YOSHIHISA ITOH l, TADASHI KAWAI I and KOHEI SHIOIRI-NAKANO Departments of Medical Biology and Parasitology, and 1 ClinicalPathology, Jichi Medical School, Tochigi-ken 329-04, Japan (Received 16 March 1981, accepted 6 July 1981) A rapid and simple latex fixation test (LFT), which quantifies immunoglobulin (Ig) released into culture supernatants is described. Latex particles are coated with rabbit anti-human IgG, IgA or IgM antibodies. With this LFT technique the concentration of Ig is determined within a few minutes. The LFT is as sensitive and quantitative as double- antibody radioimmunoassay and is capable of detecting 35, 68 and 225 ng/ml of IgG, IgA and IgM, respectively. INTRODUCTION Functional analysis of human B lymphocytes has been greatly facilitated by the use of polyclonal B cell activators. Activation of B lymphocytes has been assessed by cytoplasmic immunoglobulin (Ig) synthesis, direct or indirect plaque formation (Fauci and Pratt, 1976; Bird and Britton, 1979; Fauci, 1979), and determination of Ig released in culture supernates by radioimmunoassay (Waldmann et al., 1974). Although radioimmunoassay is commonly used for quantification of released Ig, it is rather cumbersome and time-consuming to establish and perform. We report in this paper a simple, rapid and reliable method for qualitative and quantitative determina- tion of released Ig by a latex fixation test (LFT). MATERIALS AND METHODS Preparation of anti-Ig sera Anti-human Ig antisera were raised in rabbits and purified by passage through immunoadsorbents. For immunization, 2 mg of purified Ig were emulsified with an equal volume of Freund's complete adjuvant (Difco Labo- ratories) and injected subcutaneously biweekly. The animals were bled after 2--3 months and antisera obtained. Antiserum specific for human IgG was Correspondence should be sent to: Dr. Tadashi Kasahara, Department of Medical Biology and Parasitology, Jichi Medical School, Tochigi-ken 329-04, Japan. 0022-1759/81/0000--0000/$02.75 © 1981 Elsevier/North-Holland Biomedical Press