The dynamic changes of the specific IgA and IgG antibodies in the tear of guinea pigs infected with Shigella flexneri 2a were observed with BA-ELISA.It was found that the specific IgA and IgG antibodies in the tear appeared at 8th day and reached the peak at 15th day after the challenge of the cornea of guinea pigs with the viable bacterial cells.The eyes recovered from keratoconjunctivitis were re-challenged on days 35th,45th,60th,70th,90th after the first challenge.The specific antibody levels in tear appeared much earlier and higher and reached the peak on the 15-20th day and lasted to 30th day.These are the characteristics of a secondary immune response. Eyes recovered from keratoconjunctivitis showed resistance to the secondary challenge.