Monoclonal anti-human IgG is derived from the hybridoma1 produced by the fusion of mouse myeloma cells and splenocytes from an immunized mouse. It is specific for the whole human IgG molecule, has no across action with human IgM molecule as determined by an ELISA. Reactivity is observed with all human IgG subclasses but not with the Fab fragment of human IgG, the antibody site is located in the terminal end of human IgG (part of the Fab fragment), the Fc portion has various important functions such as complement fixation, site for rheumatoid factor.