cd45作用既然是白细胞共同抗原,为什么参与T细胞信号转导,而不参与B细胞转导

CD45存在于除红细胞和浆细胞以外的所有血细胞.
它在T,B细胞上的不同作用是因为不同的CD45RA,CD45RB,CD45RC,CD45RAB,CD45RAC,CD45RBC,CD45R0,CD45R (ABC) 这些Isoform导致的
这里又段文献,描述的很详细了
CD45RA is located on naive T cells and CD45R0 is located on memory T cells.CD45 is also highly glycosylated.CD45R 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.B220 expression is not restricted to B cells and can also be expressed on activated T cells,on a subset of dendritic cells and other antigen presenting cells.
Naive T lymphocytes express large CD45 isoforms and are usually positive for CD45RA.Activated and memory T lymphocytes express the shortest CD45 isoform,CD45R0,which lacks RA,RB and RC exons.This shortest isoform facilitates T cell activation.
The cytoplasmic domain of CD45 is one of the largest known and it has an intrinsic phosphatase activity that removes an inhibitory phosphate group on a tyrosine kinase called Lck (in T cells) or Lyn/Fyn/Lck (in B cells) and activates it.

细胞间特异性识别吧。
同类有同类信息传递识别系统。