Serologic and cellular cross-reactivity of fractions of Mycobacterium intracellulare (Battey). 
Sonicates of Mycobacterium intracellulare grown in synthetic medium were separated into ammonium sulfate (50%) precipitable and nonprecipitable fractions.  Gel filtration of the precipitable fraction through columns of Sephacryl S-300 resulted in four fractions labeled A, B, C and D in order of elution.  Fractions C and D were further fractionated into 12 and 13 subfractions, respectively.  The subfractions were examined for reactivity by rocket immunoelectrophoresis (R-IE) procedures and by skin tests in homologously and heterologously immunized guinea pigs (M. kansasii, M. fortuitum, M. marinum, M. scrofulaceum and M. bovis).  Extensive sharing of antigenic determinants was observed for all of the reactive subfractions by R-IE.  None of the subfractions showed significant skin test specificity.  Possible reasons for the nonspecificity are discussed.