Abstract: Objective To define the concentration and immunity biological significance of IgM and C_1q of two determined circulating immune complexes(IgM/C_1q -TCIC) in pulmonary tuberrculosis'(TB) patients.Methods Using goat IgG anti-human C_1q for coated antibody,HRP-goat IgG anti-human IgM for detected antibody.A capture ELISA method was established to detect IgM/C_1q-TCIC of 127 cases of TB,25 cases of lung cancer,27 cases of pneumonia.Results The levels of serum IgM/C_1q-TCIC in patients with pneumonia disease placed in order were TBlung cancerpneumonia.The amount of IgM/C_1q-TCIC in TB patients had no relation to age,sex,Ig,C₃,ALT and the other clinical indicator,which was related to first or further treament and active or nonactive periods.Conclusion IgM/C_1q-TCIC in TB patients was an protecting reaction of eliminating antigens of bodies,which was closely related to immunity reactivity.IgM/C_1q-TCIC could be an useful index to evaluate the whole body immune reaction.