and expression intensity (MFI). Cross-linking of 2B4 had diverse effects depending on 2B4 expression levels. Expression of 2B4 and SAP correlated inversely, cells with high 2B4 expression showed a lower SAP content than 2B4lo cells and vice versa. Expression of SAP could be modulated by cytokine stimuli as expression intensity increased after 6 hours of incubation with IL-2 or IFNa. However, on continuous stimulation the SAP content decreased after 12 hours leading to a low expression level during following time points. Interestingly, 2B4hi cells showed a stronger loss of SAP after 12 hours as compared to 2B4lo cells. Conclusion: Cross-linking of 2B4 has diverse effects on CD8+ T cells either leading to increase or decrease of function. This regulation of CD8+ T cell function via 2B4 seems to be achieved through modulation of SAP expression possibly determining the outcome of 2B4 engagement.