BackgroundRheumatic heart disease (RHD) is one of the classic diseases that are affected by environmental and individual factors. Itself is one of the sequela of acute rheumatic fever (ARF) in adolescence and ARF is induced by the infection of streptococcus. The susceptibility of ARF and RHD not only relates with streptococcus contact and the prophylaxis after streptococcus infection, but also relates with the individual immunogenitic predisposition. It may have some important social values to study the immunogenitic and environmental predispositions and provide guidelines for the individualized prophylaxis and treatment of RHD in the developing countries such as China. This experimental study focuses on the relationship between the episode of RHD and the gene mutations and serum protein variations of an innate immuno-molecular mannose-binding lectin (MBL). MBL can specifically recognize and bind pathogenic microbial, and eliminate them by activating the complement system or acting as an opsonin to assistant the phagocytosis of lymphocytes. Congenital insufficiency of MBL may result in repeated infections in children. Its high affinity to rheumatogenic group A beta haemolyticus streptococcus purports that there may be some relationships between the susceptibility of RHD and the congenital insufficiency of MBL. It is known that there are single nucleotide polymorphisms (SNP) in the DNA sequence of MBL gene, which includes several site mutations in the first exon and promoter sequence. These site mutations result in the significant differences of MBL concentration and function among individuals. It is the aim of this experimental study to elucidate whether these differences may affect the individual susceptibility to RHD. Besides that, the possibility of MBL protein expression in E.coli and mice liver tissue was also studied, which might provide some primary experimental study results to guide the clinical therapy with MBL protein and gene.Part 1 Purification of human mannose-binding lectin (hlCL) and preparation of rabbit anti-hMBL antiserumAim To purify hMBL from mixed human surum and prepare rabbit anti-hMBL anitserum. Hethods Affinity chomatography, SDS-PAGE and SDS-PAGE gel scanning were used to purify and identify hMBL protein. New Zealand rabbits were immunized with the purified hMBL to obtain rabbit anti-hMBL antiserum. ELISA and Western blot were used to identify its liter and recognition specificity to hMBL. Results Four hundred and twenty seven microgram hMBL protein was obtained with the purity as 72%. The 32KD proteinband was cut down and used to immunize New Zealand rabbit after the purified hMBL performed SDS-PAGE. Antiserum was obtained after 6 immunizations; the titer was 1:3200 according to ELISA examination. A single band protein with its molecular weight as 32KD from human serum could be recognized specifically by the antiserum according to Western blot result, which indicated that the antiserum could specifically recognize human MBL. Cone I us i on hMBL and rabbit anti-hMBL antiserum were successfully prepared and they could be used as tools to study MBL associated human disease.Part 2 The relationship between rheumatic heart disease and the serum content of mannose binding lectinAim To investigate the relationship between rheumatic heart disease (RHD) and the serum content of mannose binding lectin (MBL). Methods ELISA was used to determine the MBL concentration in serum from 65 patients suffered from RHD and 51 normal people. Results The sex and age composition had no difference between the two groups. The serum MBL concentrations of RHD patients and normal people were 1.15+0.73 mg/L and 1.52+0.93 mg/L respectively (PO.05). Patients could be divided into two groups according to the age of the syndromes of RHD presentation, with the average syndrome-onset-age as standard. The MBL concentration in the serum of the younger group and older group were 0.82+0.50 mg/L and 1.49 + 0.79 mg/L respectively (PO.01). Conclusion Low serum MBL concentration may be a predisposition of rheum