D3114/63 is a hybridoma cell line producing a monoclonal antibody that appears to recognize a common antigenic determinant associated with the teichoic acids of Streptococcus pneumoniae. This hybridoma was produced in a fusion of splenic lymphocytes from an X-linked immunodeficient (xid) male (CBA/NxBALB/c)F1 mouse hyperimmunized with a heat-killed type 6A strain EF-3114. Treatment of EF-3114 with periodate, but not with protease, destroyed its ability to bind D3114/63. The specificity of D3114/63 for teichoic acids was suggested by the ability of both C-polysaccharide and F-antigen to inhibit its binding to EF-3114. Inhibition studies indicated that D3114/63 does not bind the PC determinant of teichoic acids. As in the case with anti-PC antibodies, the presence of an intact pneumococcal capsule significantly reduced the binding of D3114/63 to viable pneumococci. By means of a colony immunoblot procedure, it was determined that D3114/63 bound to all 97 pneumococcal strains tested including representatives of 24 different serotypes. Both D3114/63 and anti-PC antibodies were able to detect pneumococcal antigen in spinal fluids of 3 out of 4 patients with pneumococcal meningitis. D3114/63 protected mice from fatal infection with type 3 strain WU2 pneumococci but not from type 5 strain DBL5 or type 6A strain EF-3114.