Gonococcal growth factors in tissue cultures.

Growth of Neisseria gonorrhoeae in the presence of Rhesus monkey kidney (RE2) cells containing Eagle's minimal essential medium (MEM) 'conditioned' by 18-20 h of contact with RE2 cells began 3-4 h after inoculation and by 16-20 h had reached a maximum. When 'conditioned' medium (CM) was removed from the tissue cells and replaced with fresh medium a 5-6 h lag period occurred before multiplication of gonococci began and by 16 h growth was also near a maximum. CM removed from tissue cells supported the growth of six strains of N. gonorrhoeae. Three strains failed to grow in CM but multiplied when tissue cells were present. None of the strains grew in the presence of tissue cells killed by heating or in tissue-culture medium alone. Of the six strains of N. gonorrhoeae which grew in CM, three kept as their major (90%) population T1 colonies, while the remaining strains produced T1 organisms and T1A, T3, and T4 colonial variants. These results indicate that tissue cells secrete growth factors which support the growth and maintenance of T1 colonial forms of certain strains of N. gonnorhoeae.