PT - JOURNAL ARTICLE AU - Han, S AU - Hathcock, K AU - Zheng, B AU - Kepler, T B AU - Hodes, R AU - Kelsoe, G TI - Cellular interaction in germinal centers. Roles of CD40 ligand and B7-2 in established germinal centers. DP - 1995 Jul 15 TA - The Journal of Immunology PG - 556--567 VI - 155 IP - 2 4099 - http://www.jimmunol.org/content/155/2/556.short 4100 - http://www.jimmunol.org/content/155/2/556.full SO - J. Immunol.1995 Jul 15; 155 AB - Costimulatory interactions between T and B lymphocytes are crucial for T cell activation and B cell proliferation and differentiation. We have compared the roles of CD40L and B7-2 in the initiation and maturation of humoral immunity by administering anti-CD40 ligand (L) or anti-B7-2 Ab during the early (days -1 to 3) or late (days 6-10) phases of primary responses to thymus-dependent (Td) and -independent (Ti) Ags. Germinal center (GC) formation in response to a Td Ag was inhibited completely by the early administration of anti-CD40L or anti-B7-2 Abs. Later in the response, established GCs remained sensitive to anti-CD40L but were resistant to treatment with anti-B7-2. However, Ig hypermutation was reduced dramatically in GCs of anti-B7-2-treated mice and humoral memory was impaired. Early administration of anti-CD40L reduced serum Ab levels to approximately 10% of controls, whereas early treatment with anti-B7-2 reduced Ab production by only 50%. Later treatments with either Ab had no effect on Ab production. Response to a type II Ti Ag was more resistant than Td responses to interruption of costimulatory interactions. Our findings suggest that the costimulatory roles of CD40:CD40L and B7-2:CD28/CTLA-4 differ in the GC; administration of anti-CD40L abrogates an established GC reaction, whereas Ab to B7-2 suppresses Ig hypermutation and entry into the B cell memory compartment. Once B cells have entered the differentiation pathway to Ab production, neither CD40L nor B7-2 is necessary for their continued differentiation and persistence.