Changes in lymphocyte antigen gene nomenclature from Ly5 to Ptprc

Although the genetic nomenclature for loci controlling mouse lymphocyte antigens changed a few decades ago, researchers still use the term Ly5 quite often. The correct nomenclature for this locus, however, is Ptprc (protein-tyrosine phosphatase, receptor type c). This article reviews the history of this locus and its confusing nomenclature.

First: Ly5

In 1975 K. Komura, K. Itakura, E. A. Boyse, and M. John (1) described an antigen found on T-lymphocytes. The antigenic specificity found on C57BL/6 cells was named Ly5.1 and the specificity on SJL/J cells Ly5.2. Gene naming convention for alleles has been to assign a superscript "a" to the locus symbol for a gene that determines the ".1" specificity and superscript "b" for the ".2" specificity. Consequently, the C57BL/6 allele became Ly5a and the SJL/J allele became Ly5b.

In 1977, E. A. Boyse and colleagues (2) suggested a revised nomenclature for lymphocyte antigens that would distinguish B-cell from T-cell antigens. Under this recommendation,  Ly5 would have become Lyt4. This apparently was not universally accepted, as "Ly5" continued to appear in the literature.

In 1987,  H. C. Morse III, F-W. Shen, and U. Hämmerling (3) presented a revised version of nomenclature rules governing mouse lymphocyte antigens. They recommended following the practice of designating C57BL/6 alleles with the superscript "b." The allele and antigen designations of the Ly5 alleles for C57BL/6 and SJL/J, then, were reversed; the C57BL/6 allele became Ly5b (antigenic specificity Ly5.2) and SJL/J became Ly5a (antigenic specificity Ly5.1).

Next: CD45

In 1992 H. C. Morse III (4) presented a further revision of nomenclature governing cell surface antigens whereby Ly5 became Cd45.  The nomenclature recommendations authored by Morse and colleagues were approved by the International Committee on Standardized Genetic Nomenclature for Mice. Therefore, the antigen specificities encoded by the CD45 alleles for C57BL/6J and SJL/J became CD45.2 and CD45.1, respectively. 

Now: Ptprc

The current use of the Ptprc designation for Cd45 was based on work in humans following the report of Charbonneau and colleagues (5) who first showed that a protein-tyrosine phosphatase (human placental protein-tyrosine phosphatase 1B) was homologous to the CD45 protein. Ptprc is one of a family of protein-tyrosine phosphatase genes involved in the regulation of cell growth.

The table below summarizes the old and currently accepted nomenclature for the Ly5/CD45/Ptprc alleles and antigen specificities for C57BL/6J (000664), SJL/J (000686) and the commonly used C57BL/6J Ly5a/CD45.1/Ptprca congenic strain, B6.SJL-Ptprca Pepcb/BoyJ (002014).


1. Komura, K., K. Itakura, E. A. Boyse, and M. John. 1975. Ly-5: a new lymphocyte antigen system. Immunogenetics 1:452-456.

2. Boyse, E.A., H. Cantor, F-W. Shen, and I.F.C. McKenzie. 1977. Nomenclature for antigens demonstrable on lymphocytes. Immunogenetics 5:189.

3. Morse H.C. III, F-W. Shen, and U. Hämmerling. 1987. Genetic nomenclature for loci controlling mouse lymphocyte antigens. Immunogenetics 25:71-78.

4. Morse H.C. III. 1992. Genetic nomenclature for loci controlling surface antigens of mouse hemopoietic cells. J. Immunol. 149:3129-3134.

5. Charbonneau, H., N.K. Tonks, K.A. Walsh, and E.H. Fischer. 1988. The leukocyte common antigen (CD45): a putative receptor-linked protein tyrosine phosphatase. Proc. Nat. Acad. Sci. 85:7182-7186.