, 2011). Variations in serum levels of collectins have been implicated in various immunity disorders. Functional mannose-binding lectin (MBL) deficiency, caused by single-nucleotide polymorphisms in the coding region of the MBL2 gene, has been associated with increased susceptibility to infections in young children and immunocompromised individuals ( Sumiya et al., 1991, Garred et al., 1997, Summerfield

et al., 1997, Neth et al., 2001 and Peterslund et al., 2001). MBL deficiency or low MBL serum levels are also associated with the occurrence of autoimmune disorders, such as systemic lupus erythematosus (SLE) ( Lee et al., 2005). Circulatory levels of the otherwise lung-associated collectin surfactant protein D (SP-D) are increased upon lung injuries ( Leth-Larsen Sirolimus datasheet et al., 2003). Low serum levels of SP-D, caused by the variant allele Thr11, may increase susceptibility click here to tuberculosis ( Floros et al., 2000). Low serum levels of SP-D have also been implicated

in pathogenesis of SLE ( Hoegh et al., 2009). In order to identify the biological functions of CL-11, it is necessary to be able to measure CL-11 levels in serum and other fluids. The objectives of the present work were to develop and validate an enzyme-linked immunosorbent assay (ELISA) for measuring human CL-11 in various samples, and to determine CL-11 levels in normal serum and plasma. Unless otherwise stated, reagents were obtained from Sigma-Aldrich (Vallensbaek, Denmark). The following buffers were used: TBS: (10 mM Tris and 145 mM NaCl, pH 7.4), coating buffer (15 mM Na2CO3, 35 mM NaHCO3, pH 9.6),

washing buffer for ELISA (TBS, fantofarone 5 mM EDTA, 0.05% Emulfogen, pH 7.4), substrate buffer (35 mM citric acid, 67 mM Na2HPO4, 0.012% H2O2, pH 5.0), washing buffer for Western blotting (TBS, 5 mM EDTA, 0.1% Emulfogen, 5% non-fat dried milk, 0.1% w/v BSA, pH 7.4). The expression and purification of recombinant CL-11 were performed as previously described (Hansen et al., 2010). Briefly, full-length untagged human CL-11 was expressed in DG44 CHO cells using the bicistronic pOptiVEC TOPO vector (Invitrogen, Taastrup, Denmark). Recombinant CL-11 was purified from the culture supernatant using mannose-Sepharose affinity purification. The concentration of CL-11 was measured by quantitative amino acid analysis of 7 different fractions of purified CL-1 from three different rounds of purification. The derived average conversion factor of the 7 analyses was used throughout the study. Monoclonal antibodies (MAbs) were essentially produced by the principles described by Kohler and Milstein (Kohler and Milstein, 1975) in outbred NMRI mice with modifications previously described (Hansen et al., 2008). Briefly, purified recombinant CL-11 was used as the antigen. Positive clones were identified by ELISA using microtiter plates coated with CL-11. Cells from the positive wells were cloned at least four times by limiting dilution.