CD22, or cluster of differentiation-22, is a molecule belonging to the SIGLEC family of lectins. It is found on the surface of mature B cells and to a lesser extent on some immature B cells. Generally speaking, CD22 is a regulatory molecule that prevents the overactivation of the immune system and the development of autoimmune diseases. CD22 is a sugar binding transmembrane protein, which specifically binds sialic acid with an immunoglobulin (Ig) domain located at its N-terminus. The presence of Ig domains makes CD22 a member of the immunoglobulin superfamily. CD22 functions as an inhibitory receptor for B cell receptor (BCR) signaling. Mediates B-cell B-cell interactions. May be involved in the localization of B-cells in lymphoid tissues. Binds sialylated glycoproteins; one of which is CD45. Preferentially binds to alpha-2,6-linked sialic acid. The sialic acid recognition site can be masked by cis interactions with sialic acids on the same cell surface. Upon ligand induced tyrosine phosphorylation in the immune response seems to be involved in regulation of B-cell antigen receptor signaling. Plays a role in positive regulation through interaction with Src family tyrosine kinases and may also act as an inhibitory receptor by recruiting cytoplasmic phosphatases via their SH2 domains that block signal transduction through dephosphorylation of signaling molecules.
Background References
1. Hatta Y, Tsuchiya N, Matsushita M, Shiota M, Hagiwara K, Tokunaga K (April 1999). "Identification of the gene variations in human CD22". Immunogenetics. 49 (4): 280–6.
2. Lee M, Kiefel H, LaJevic MD, Macauley MS, Kawashima H, O\'Hara E, et al. (October 2014). "Transcriptional programs of lymphoid tissue capillary and high endothelium reveal control mechanisms for lymphocyte homing. Nature Immunology. 15 (10): 982–95.
Sequence Similarity
Belongs to the immunoglobulin superfamily. SIGLEC (sialic acid binding Ig-like lectin) family.
Tissue Specificity
B-lymphocytes.
Post-translational Modification
Phosphorylation of Tyr-762, Tyr-807 and Tyr-822 are involved in binding to SYK, GRB2 and SYK, respectively. Phosphorylation of Tyr-842 is involved in binding to SYK, PLCG2 and PIK3R1/PIK3R2.; Phosphorylated on tyrosine residues by LYN.
Western blot analysis of CD22 on different lysates with Mouse anti-CD22 antibody (EM1902-13) at 1/5,000 dilution.
Lane 1: Daudi (Human Burkitt's lymphoma cell) cell lysate Lane 2: Raji (Human Burkitt's lymphoma cell) cell lysate Lane 3: Ramos (Human Burkitt's lymphoma cell) cell lysate Lane 4: Jurkat (Human T-lymphoblastic cells) cell lysate(negative)
Lysates/proteins at 15 µg/Lane. Exposure time: 12 seconds; ECL: K1801
Blocking: 5% NFDM/TBST, 1 hour at room temperature Primary antibody: EM1902-13, 1/5,000 in primary antibody dilution buffer (K1803), overnight at 4 ℃ Secondary antibody: Goat anti-Mouse IgG-HRP (HA1006), 1/50,000 in 5% NFDM/TBST, 1 hour at room temperature
Predicted band size: 95 kDa Observed band size: 140 kDa
Immunohistochemical analysis of paraffin-embedded human spleen tissue using anti-CD22 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (EM1902-13, 1/1000) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Flow cytometric analysis of CD22 was done on Daudi cells. The cells were fixed, permeabilized and stained with the primary antibody (EM1902-13, 1/100) (red). After incubation of the primary antibody at room temperature for an hour, the cells were stained with a Alexa FluorTM488 Goat anti-Mouse IgG Secondary antibody at 1/500 dilution for 30 minutes.Unlabelled sample was used as a control (cells without incubation with primary antibody; black).
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