This may claim that the properties of synovial surfactant were somewhat different from those of pulmonary surfactant and do not require the presence of SP-B. 6.1-fold increase in SP-D concentrations. Total protein content in the synovial fluid samples from patients with rheumatoid arthritis showed a 2.1-fold increase and phospholipid content showed 7.0-fold increase in comparison with samples of healthy synovial fluid. Rheumatoid factor, CRP, IgA, IgM, and IgG concentrations in synovial fluid samples from patients with rheumatoid arthritis were 40-2660 KIU/L, 4-35 mg/L, 0.10-2.70 g/L, 0.50-1.90 g/L, and 5.3-15.4 g/L respectively. Conclusion SP-A and SP-D were present and expressed in various degrees in the synovial fluid of patients with rheumatoid arthritis. SP-A and SP-D may play role in the initiation of immune system and joint inflammation, and may be an integral component of synovial fluid and provide insights for in innate and adaptive immunity within the joint. Pulmonary surfactant is mainly a mixture of lipids and proteins, which covers the PF-4191834 peripheral airway. Surfactant in the lungs has two distinct functions. It reduces the surface tension at the air-liquid interface of the lung (1) and plays a role in host defense against contamination and inflammation (2). About 10% of surfactant consists of proteins. So far, 4 surfactant proteins (SP) have been defined C SP-A, SP-D, SP-B, and SP-C. SP-B and SP-C are small and extremely hydrophobic proteins. SP-A and SP-D are users of the collectin family of proteins containing collagen regions (3); they play important roles in host defense mechanisms and mediation of immune cell functions of the lung (4). The main site of surfactant biosynthesis is the lung, although surfactant protein mRNA and, in some cases, proteins have been found at non-pulmonary sites (5). SP-A and SP-D have been localized to non-pulmonary sites including the small intestines, colon and intestinal lumen mesenteric cells (6), lung, heart, belly, kidney (7), gastric mucosa, Eustachian tube (8,9), brain, testis, pancreas, salivary gland, heart, prostate, small intestine, placenta (10), human skin (11), female genital tract, the placenta and amniotic fluid (12), vaginal mucosa, vaginal lavage fluid (13), and synovial fluid (14-17). There may be a correlation between the presence of lamellar body and surfactant protein secretion in the synovium (18). Lamellar body are specialized intracellular organelles PF-4191834 of epithelial cells for packaging and secretion of surfactant (14). Dobbie et al (19) and Schwarz and Hills (20) reported the presence of lamellar body in type B synoviocytes, and synovial B cells seem to be the source and secretion site of synovial surfactant within the joint. Dobbie et al (19) also found an SP-A-like protein in human synovium, which provided a new physiological and pathological insight into these tissues and suggested that this lamellar bodies present in synovium type B cells were the major targeted cytoplasmic organelle in rheumatoid diseases. Additionally, it was reported that SP-A, as expressed by immunoglobulin G (IgG) and autoantibodies, was present in the synovial fluid isolated from patients with rheumatoid arthritis (16). In the lung, surfactant proteins assist in the formation of a monolayer of surface-active phospholipid at the liquid-air interface of the alveolar lining, reducing the surface tension (21). In contrast, surface-active phospholipid adsorbed to articular surfaces has been identified as the load-bearing boundary lubricant of the joint (22). This raises the question whether or not surfactant proteins in the synovial fluid are an integral part of normal joints. The hypothesis in this study was that surfactant proteins may play a significant role in the functioning of joints. The aim was to determine the presence of SP-A and SP-D in the synovial fluid from patients with rheumatoid arthritis and healthy controls and to correlate the changes in synovial fluid SP-A and SP-D concentration with rheumatoid factor, C-reactive protein (CRP), IgA, IgM, IgG, total protein, and total lipid PF-4191834 content. Material and methods The experimental protocol for this study was approved by the SSV Human Subjects Review Committee at the University or college of Queensland, PF-4191834 Brisbane, Queensland, Australia. Preparation of human lung bronchoalveolar lavage fluid Three bronchoalveolar lavage (?~?0.5 mL) samples were collected from patients undergoing lung lavage at Princess Alexandra Hospital (Brisbane, QLD, Australia) and diluted.