FIG. 3.

Protein L targets B-cell subpopulations involved in innate immunity. Lymphoid cell subpopulations were identified by immunofluorescence staining in control (untreated) and in HEL- and protein L-treated transgenic mice. (A) Splenocytes were triple stained with CyChrome-labeled anti-mouse B220 MAb, FITC-labeled anti-mouse CD21 MAb, and PE-labeled anti-mouse CD23 MAb. Lymphoid cells were gated on the B220-expressing cells. MZ (B220⁺ CD23^−/low CD21⁺) but not FO (B220⁺ CD23⁺ CD21⁺) B cells are reduced in protein L-treated mice. (B) Lymph node cells were stained with PE-labeled anti-mouse CD4 and FITC-labeled anti-mouse CD8 MAbs. The treatments do not affect T lymphocytes. (C) Peritoneal B1 cells are reduced in protein L-treated mice.