CD22 is a 130 kD type 1 transmembrane glycoprotein, also called Siglec-2 and the BL-CAM. It is part of the superfamily immunoglobulin (sialoadhesin subgroup). You can know more about CD22 antibodies via

CD22 - Wikipedia

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CD22 is found inside the cells of proB and B cells. It is also expressed in the B cell surface on mature cells and activated B cells however, it is not expressed in plasma cells. 

CD22 is found within the B-cell receptor complex, and it is associated with the SHP-1 receptor, Syk, Lck, Lyn, and phospholipase cg1. 

The primary function of CD22 is believed to lie in the limitation of the antigen receptor's signaling through altering the threshold for activation of B cells. 

CD22 has been demonstrated to be a ligand for CD45RO and CD75 however the actual binding partners for this molecule are in debate.

It is known that the CD22 antigen is not present in peripheral blood T lymphocytes, granulocytes, and monocytes. It is found on less than one percent of bone marrow-derived mononuclear cells and a 50percent of Epstein Barr virus-transformed lymphoblastoid B cell varieties. 

CD22 is a heterogeneous marker on B lymphocytes of peripheral blood. The antigen is destroyed after activation of B cells by mitogens of various kinds. The CD22 protein regulates signal transmission via the receptor for B cells.