The CD45 protein family consists of multiple members that are all products of a single complex gene. This gene contains 34 exons, producing a massive protein with extracellular and cytoplasmic domains that are both unusually large. Exons 4, 5, and 6 (corresponding to protein regions A, B, and C) are alternatively spliced to generate up to eight different protein products featuring combinations of zero, one, two, or all three exons. CD45's large extracellular domain is highly glycosylated, and these eight isoforms allow wide variation in the structure of its side chains. The isoforms affect the protein's N-terminal region, which extends linearly out from the cell and bears the O-linked glycan chains. CD45 isoforms show cell-type and differentiation-stage specific expression, a pattern which is quite well conserved in mammals. These isoforms are often used as markers that identify and distinguish between different types of immune cells. Naive T lymphocytes are typically positive for CD45RA, which includes only the A protein region. Activated and memory T lymphocytes express CD45RO, the shortest CD45 isoform, which lacks all three of the A, B, and C regions. This shortest isoform facilitates T cell activation. CD45R (also known as CD45RABC) contains all three possible exons. It is the longest protein and migrates at 200 kDa when isolated from T cells. B cells also express CD45R with heavier glycosylation, bringing the molecular weight to 220 kDa, hence the name B220 (B cell isoform of 220 kDa).
Background References
1. Naik S et al. Selective depletion of naive T cells by targeting CD45RA. Front Oncol. 2023 Jan
2. Bremm M et al. Depletion of CD45RA(+) T cells: Advantages and disadvantages of different purification methods. J Immunol Methods. 2021 May
Flow cytometric analysis of human peripheral blood lymphocytes labeling Human CD45RA.
Cells were stained with the primary antibody (HA601341, 1μg/mL) (red). After incubation of the primary antibody at +4℃ for an hour, the cells were stained with a iFluor™ 488 conjugate-Goat anti-Mouse IgG Secondary antibody (HA1125) at 1/1,000 dilution for 30 minutes at +4℃. Unlabelled sample was used as a control (cells without incubation with primary antibody; blue).
Immunocytochemistry analysis of Jurkat cells labeling Human CD45RA with Mouse anti-Human CD45RA antibody (HA601341) at 1/100 dilution.
Cells were fixed in 4% paraformaldehyde for 15 minutes at room temperature, permeabilized with 0.1% Triton X-100 in PBS for 15 minutes at room temperature, then blocked with 1% BSA in 10% negative goat serum for 1 hour at room temperature. Cells were then incubated with Mouse anti-Human CD45RA antibody (HA601341) at 1/100 dilution in 1% BSA in PBST overnight at 4 ℃. Goat Anti-Mouse IgG H&L (iFluor™ 488, HA1125) was used as the secondary antibody at 1/1,000 dilution. PBS instead of the primary antibody was used as the secondary antibody only control. Nuclear DNA was labelled in blue with DAPI.
beta Tubulin (ET1602-4, red) was stained at 1/100 dilution overnight at +4℃. Goat Anti-Rabbit IgG H&L (iFluor™ 594, HA1122) were used as the secondary antibody at 1/1,000 dilution.
Immunocytochemistry analysis of Raji cells labeling Human CD45RA with Rabbit anti-Human CD45RA antibody (HA601341) at 1/500 dilution.
Cells were fixed in 4% paraformaldehyde for 15 minutes at room temperature, permeabilized with 0.1% Triton X-100 in PBS for 15 minutes at room temperature, then blocked with 1% BSA in 10% negative goat serum for 1 hour at room temperature. Cells were then incubated with Rabbit anti-Human CD45RA antibody (HA601341) at 1/500 dilution in 1% BSA in PBST overnight at 4 ℃. Goat Anti-Rabbit IgG H&L (iFluor™ 488, HA1121) was used as the secondary antibody at 1/1,000 dilution. PBS instead of the primary antibody was used as the secondary antibody only control. Nuclear DNA was labelled in blue with DAPI.
Beta tubulin (HA601187, red) was stained at 1/100 dilution overnight at +4℃. Goat Anti-Mouse IgG H&L (iFluor™ 594, HA1126) was used as the secondary antibody at 1/1,000 dilution.
Immunohistochemical analysis of paraffin-embedded human lymph nodes tissue with Mouse anti-Human CD45RA antibody (HA601341) at 1/5,000 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (HA601341) at 1/5,000 dilution for 1 hour 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.
Immunohistochemical analysis of paraffin-embedded human tonsils tissue with Mouse anti-Human CD45RA antibody (HA601341) at 1/5,000 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (HA601341) at 1/5,000 dilution for 1 hour 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.
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