Absence of early complement components (C1-C4) results in inability of immune complexes to activate the cascade. These patients have increased susceptibility to infections with encapsulated micro-organisms. They may also develop symptoms suggestive of autoimmune disease.C3 deficiency may result in Pneumococcal and Neisserial infections and Autoimmune glomerulonephritis. C4 deficiency has been associated with SLE & Glomerulonephritis.