GERMINAL CENTER T-CELLS EXHIBIT PROPERTIES OF MEMORY HELPER T-CELLS

Potential roles of germinal center (GC) T cells in immune memory were investigated by examining T cells in GCs lymph nodes (LNs) following i mmunization with myelin basic protein (MBP), MBP preferentially stimul ates T cells expressing the V(beta)8 TCR family in B10.PL mice. By sta ining lymph nodes with peanut agglutinin, GCs were first identified 8 days after immunization and could still be detected 50 days later, Whe n T cells within GCs were examined at Day 8, the majority (>90%) were CD45RB-negative and a large percentage (20%) had already proliferated several days before as determined by bromodeoxyuridine (BrdU) incorpor ation, When BrdU(+) V(beta)8(+) cells were examined in various areas o f LNs 3 and 8 weeks after immunization, BrdU(+) V(beta)8(+) cells were approximately fourfold more frequent in GCs than other areas of LNs. When GCs were examined for IL-4 mRNA(+) cells using an in situ hybridi zation method, only 0.01% of GC cells expressed IL-4 mRNA, correspondi ng to about 1% of GC T cells, Shortly following restimulation with MBP , the frequency of cells expressing IL-4 mRNA increased fivefold. Take n together, these findings indicate that GC T cells possess characteri stics associated with memory T cells. (C) 1995 Academic Press, Inc.