The Lectin Jacalin Specifically Triggers Cell Signaling in CD4+T Lymphocytes

The lectin jacalin was shown to specifically stimulate CD4+lymphocytes. This lectin, which presents a peptide highly similar to a sequence of the HIV external glycoprotein, interacts with CD4 and is able to inhibitin vitroHIV infection. Since jacalin binds also CD8, its mitogenic specificity cannot exclusively be attributed to its interaction with CD4. We therefore hypothesized that the lectin could trigger signals specifically associated with CD4. Here we show that jacalin triggers IL2 gene transcription only in CD4+lymphocytes. In parallel, we show that numerous proteins are tyrosine phosphorylated in this cell subset while only a restricted number of them are phosphorylated in CD8+cells. Moreover, we show that the tyrosine kinase p56lck, which is associated with both CD4 and CD8, is activated only in CD4+lymphocytes, making this lectin a good model for the study of cell signaling triggered in this restricted subpopulation.