Figure 4: Proteins specifically expressed in the hematopoietic lineage. Examples of proteins expressed in the hematopoietic lineage tissues. Among the significantly up-regulated proteins in the hematopoietic lineage tissues are well known CD markers such as PTPRC (CD-45). CD-45 is expressed in virtually all lymphoid cells, exemplified by two different antibodies from the top 100 list showing expression in lymph node tissues (A and C). The tyrosine protein kinase BTK, a protein known to play a crucial role in B-cell ontogeny, shows distinct expression in lymphoid cells of the spleen (B). The less well-characterized TCF-7, suggested as a T-cell transcription factor shows expression in lymphoid cells of T-cell areas as well as in subsets of certain epithelia including the fallopian tube (D).