[PubMed] [Google Scholar] 11. no raises were found in the IgA EIA. Only one patient showed a significant IgA antibody increase with all of the fluorescein-labeled conjugates. Five significant titer changes were recognized by at least two conjugates, and in nine instances, the titer increase was recognized by one conjugate only. The titer agreement indicated by kappa coefficients was very good or good for all the fluorescein-labeled conjugates and the EIA with low antibody titers but decreased with increasing titers. The analysis of acute illness is usually based on the demonstration of at least a fourfold increase in immunoglobulin G (IgG) antibody levels in serum samples between the acute phase and the convalescent phase or the presence of IgM antibodies in any serum sample. The microimmunofluorescence (MIF) test is considered the gold standard for the measurement of chlamydia species-specific antibodies (4, 5, 11). The part of IgA antibodies in the analysis of acute-phase illness has not been definitely founded (4), and these antibodies are not measured in all laboratories. However, the measurement of IgA antibodies offers been shown to increase diagnostic findings in some studies (5, 20). Commercial fluorescein-conjugated anti-human IgA antibodies have not been standardized, and the use of different conjugates may cause substantial variations in IgA results (29). Thus, a comparison of different commercial conjugates may help laboratories to make choices and may lead to more standardized MIF antibody findings. The removal of IgG antibodies before the measurement of IgM antibodies is generally recommended to avoid false-positive IgM findings due to the presence of IgM rheumatoid element (7). Furthermore, IgG antibodies with a high affinity may also interfere with the ROCK inhibitor-2 measurement of IgM antibodies in the immunofluorescence method (10). It was shown earlier that the removal of IgG antibodies before the measurement of IgA antibodies to by MIF makes IgA antibody reactivity better to interpret, the prozone effect disappears, and titers increase, especially in serum samples with high IgG titers (9). In the present study, we compared seven commercial ROCK inhibitor-2 fluorescein-conjugated anti-human IgA antibodies by using our in-house MIF test, one commercial MIF kit, and one commercial enzyme immunoassay (EIA) kit for the measurement of IgA antibodies in serum samples from adult and child individuals with pneumonia. For less difficult interpretation, we eliminated interfering IgG antibodies with Gullsorb reagent before the measurement of IgA antibodies by MIF. MATERIALS AND METHODS Altogether, 261 serum samples from 90 adults and 32 children with pneumonia (collected in different pneumonia studies) were originally tested with the in-house MIF test for strain L2 and strain ROCK inhibitor-2 K6 (5) as antigens. The seven commercial FITC-conjugated -chain-specific anti-human IgA antibodies used were designated as follows: Dako (Dako, Glostrup, Denmark), Kallestadt (Sanofi Diagnostics Pasteur), Zymed (Zymed, South San Francisco, Calif.), Jackson (Jackson ImmunoResearch), Caltag (Caltag, Burlingame, Calif.), Labsystems (Labsystems), and Sigma (Sigma, St. Louis, Mo.). Before assessment, ideal dilutions for the anti-human IgA conjugates were determined by using 10 IgA-positive serum samples at a 1/20 dilution in phosphate-buffered saline (PBS), and 2% Amido Schwartz counterstain was utilized for all the conjugates. In the commercial MIF kit slides, the elementary body antigens of and were treated to remove genus-specific lipopolysaccharide, while the elementary bodies of were not treated. The serum samples were tested after treatment with Gullsorb (Gull Laboratories, Salt Lake City, Utah) in accordance with the instructions of the manufacturer to remove interfering IgG antibodies (9, 27). The serum samples were tested in serial twofold dilutions, starting at 1:10, in 0.25% PBS- egg yolk sac (Labema, Kerava, Finland), except the commercial MIF kit had its own sample diluent. The patient serum samples for daily use were thawed and diluted in adequate ROCK inhibitor-2 volumes to allow simultaneous testing of all conjugates. Positive and ROCK inhibitor-2 negative control serum samples were included in all test series. Rabbit Polyclonal to ZC3H11A The commercial MIF kit included the sample diluent, the conjugate, and the settings for the test. The serum samples were.