FLOW CYTOMETRIC ANALYSIS AND IMMUNOHISTOCHEMISTRY OF DELAYED-TYPE HYPERSENSITIVITY RESPONSES IN MICE IMMUNIZED WITH RAT HEPATOCYTES

Delayed-type hypersensitivity (DTH) responses to rat hepatocytes (HCs) in mice were investigated by flow cytometric analysis and immunohisto chemistry with monoclonal antibodies directed against murine class II, CD4, and CD8 antigens. Mice were immunized subcutaneously (s.c.) with 10(6) rat HCs (referred to as s.c.-immunized mice), and control mice were injected s.c. with sterile Hanks' solution (non-immunized mice). Four days later, 10(5) rat HCs were injected into the footpad of s.c.- immunized mice and non-immunized mice. The DTH response in s.c.-immuni zed mice significantly increased after challenge when compared to that in non-immunized mice. The numbers of class II+, CD4(+), and CD8(+) c ells in the footpad, and CD4(+) and CD8(+) cells in the inguinal lymph node of s.c.-immunized mice significantly increased during the DTH re sponse. An increase in the number of CD4(+) cells in the footpad of s. c.-immunized mice after challenge was more significant than that of no n-immunized mice. The number of CD4(+) cells increased more markedly i n the footpad of s.c.-immunized mice as compared to that of CD8(+) cel ls. Furthermore, immunohistochemical studies of the footpad of s.c.-im munized mice showed more severe infiltration of CD4(+) cells rather th an CD8(+) cells at the injection site of rat HCs. These results sugges t that the DTH response in the footpad of mice immunized with rat HCs is associated with severe infiltration of CD4(+) cells.