The expression of murine alloantigens on blood lymphocytes.

Single- and two-colour immunofluorescence was used to analyse and compare the expression of 12 antigens on the surface of Ig- mouse blood lymphocytes (BL) and Ig- lymph node (LN) cells. Studies in different strains of mice showed that: (i) there were fewer Thy-1+, Ly 1+, L3T4+ cells in BL compared to LN; (ii) Ly 2+ BL showed a unique fluorescence profile with a temporal variation in antigen density not evident in LN; (iii) Thy-1- Ly 1- cells were more common in BL than LN; (iv) L3T4 and Ly 2 were present on mutually exclusive subpopulations in BL; (v) Ly 6A, (Ly 6.2), Ly 6C (Ly 28.2) Ly 28.6C and Ly 12.1 antigenic determinants were expressed on the same proportion of BL and LN cells and to the same level; (vi) Ly 24 (Pgp-1) was the only alloantigen examined where the number of positive cells was increased in BL (65%) compared to LN (40%); (vii) Ly 5 and Ly 15 (LFA-1) showed significant differences in antigen density distribution between BL and LN; (viii) Ly 21.2 was similar to Ly 15.2 expression; (ix) 20% of Ig-LN cells were Ia+, but Ia was absent from Ig-BL. Thus, BL differ in antigen distribution and density from lymphocytes in LN and other tissues and should be considered as a unique population of lymphocytes.