Phenotypic and functional differences between lymphocytes from NALT and nasal passages of mice

Nasal-associated lymphoid tissue (NALT) and nasal passages (NP) are considered as inductive and effector sites, respectively. The differences among lymphocyte populations of these nasal compartments have not been clearly established. The aim of this work was to contribute to the characterization of NALT and NP lymphocytes in mice. We isolated lymphocytes from both compartments, determined the frequencies of B220⁺ cells as well as CD8 ⁺, CD4⁺ T cells; and analysed the expression of CD69 and CD25. Besides we analysed the proportion of T cells producing IL-2, IL-4, IL-5, IL-10, IFN-γ and TNF-α. We found differences between NALT and NP. Two populations of B cells, B220+^hi and B220+^low were clearly distinguished only in NP, but not in NALT. Both ^hi and ^low B220⁺ cells expressed CD19, but only a fraction of the B220+^low population, expressed the plasma cell marker CD138 ⁺. More B than T lymphocytes, as well as higher frequencies of CD4⁺ than CD8⁺ T cells were found in both compartments. A small fraction of NK cells (CD3^-DX5⁺) along with a significant proportion of double negative CD4^-CD8^-CD3 ⁺DX5^- T cells was detected in both nasal tissues. Furthermore, as expected for a mucosal effector site, NP contained major proportions of B220⁺, T CD4⁺ and T CD8⁺ cells expressing CD25 and CD69 in comparison to NALT. Likewise, the proportion of T cells spontaneously producing IL-2, IFN-γ, and IL-4, was higher in NP than in NALT. These data provide further evidence indicating that distinctive phenotypic and functional features exist in the lymphocyte populations residing at NALT and NP.