(a)l. Antigen crosslinkage of mlg CD28 induces signal(, which leads to ncreased expression of class l MHC and co-stimulatory B7 on B cell 2. TH cell recognizes antigen class II MHC on B-cell membrane. This plus co-stimulatory signal activates TH cell Naive C+0 H cell B cell (b)l. Following activation of TH cell. it begins to express CDOL 2. Interaction of CD40 and CD4OL provides signal② 3. B7-CD28 interactions provide costimulation to the TH cell CDiO CDL B细胞 (c)l B cell begins to express receptors Cytokines 活化的 for various cytokine IL2. 1 1L.5 2. Binding of cytokines released from TH cell in a directed fashion sends 双信号 signals that support the progression of the B cell to DNA synt 途径示 Activated H cell 意图 Mite Proliferatin B cellsB细胞 活化的 双信号 途径示 意图