We have shown that the formation of an immunological synapse at the interface between a T cell and a DC was not initiated by antigen recognition, as functional synapses formed in the absence of exogenously added antigen and even in the absence of MHC1. In addition, we noticed that these synapses formed more easily with CD4+ than with CD8+ T cells, which specifically express a molecule recognized by the mAb 1B11. We suggested, therefore, a possible causal link between these two facts. We consider that 1B11 recognizes a hyperglycosylated form of CD43, whereas Ziltener and Carlow think that it recognizes an hyposialylated form of CD45RB.

Without any ambiguity it has been shown that 1B11 can recognize CD432,3,4,5, including at the surface of primary T cells in nonimmunized mice2. Ziltener and colleagues have shown that 1B11 can also bind to CD45RB, a likely reason why T cells from CD43-deficient mice are still 1B11-positive6. In a resting T cell, there is an ambiguity concerning the fraction of 1B11-labeling that is due to CD43 or to CD45RB. Before being detected by 1B11, CD45RB epitopes must be uncovered by neuraminidase treatment, as observed with either intact cells or in immunoprecipitates6.

From this finding, we concluded that the epitope recognized by 1B11 in untreated naïve CD8 T cells was most probably CD43, and not CD45RB. Admittedly, this conclusion deserves to be challenged by additional experiments. It would also be worth examining whether the presence of the molecule recognized by 1B11 (whether it be CD43 or CD45RB) is directly responsible for the relative difficulty with which CD8+ T cells form functional synapses with DCs, or whether this 1B11 labeling is only a neutral indicator of a different state of glycosylation.

See CD43 in T cell–DC conjugate formation? by Hermann J. Ziltener and the Functional antigen-independent synapses formed between T cells and dendritic cells by Patrick Revy