Role of lymphotoxin and homeostatic chemokines in the development and function of local lymphoid tissues in the respiratory tract

Los órganos linfoides secundarios tienen una posición anatómica estratégica, con la finalidad de reclutar células presentadoras de antígeno activadas, células "naïve" y poblaciones de células T y B que se encuentran recirculando en la periferia. La estructura de los órganos linfoides secundarios, la cual incluye zonas definidas de células T y B, poblaciones especiales de células estromales, vénulas del endotelio alto y vasos linfáticos, ha evolucionado para facilitar los encuentros entre células presentadoras de antígeno y linfocitos, facilitando la proliferación y diferenciación de células B y T estimuladas por antígenos. La mayoría de los mecanismos que rigen el desarrollo y organización de los órganos linfoides secundarios han sido descubiertos en la década pasada y, ayudan a concluir que las interacciones celulares y moleculares específicas para el desarrollo y organización de los órganos linfoides secundarios son ligeramente diferentes y reflejan probablemente la presencia de poblaciones celulares específicas en un lugar y tiempo adecuados. En esta revisión se discuten los mecanismos involucrados en el desarrollo, organización y función de tejidos linfoides locales del tracto respiratorio, incluidos el tejido linfoide asociado a la nariz (NALT) y el tejido linfoide inducible asociado al bronquio (iBALT)

Secondary lymphoid organs are strategically placed to recruit locally activated antigen presenting cells (APCs) as well as naïve, recirculating T and B cells. The structure of secondary lymphoid organs - separated B and T zones, populations of specialized stromal cells, high endothelial venules and lymphatic vessels - has also evolved to maximize encounters between APCs and lymphocytes and to facilitate the expansion and differentiation of antigen- stimulated T and B cells. Many of the general mechanisms that govern the development and organization of secondary lymphoid organs have been identified over the last decade. However, the specific cellular and molecular interactions involved in the development and organization of each secondary lymphoid organ are slightly different and probably reflect the cell types available at that time and location. Here we review the mechanisms involved in the development, organization and function of local lymphoid tissues in the respiratory tract, including Nasal Associated Lymphoid Tissue (NALT) and inducible Bronchus Associated Lymphoid Tissue (iBALT)

Expression and function of CD22, a B-cell restricted molecule.

In this work, we studied the expression and function of CD22 in murine B cells. CD22 has been previously characterized as an activation marker of mature B lymphocytes. However, we found that CD22 is expressed early during the ontogeny of B cells in the bone marrow and spleen, and was found on B cells isolated from all the different lymphoid compartments. We also found that B cells stimulated through the B-cell antigen receptor (BCR), CD38 and CD40, upregulated CD22 expression to maximal levels within 24 h after stimulation, but that the levels of CD22 declined at later times (48 and 72 h). CD22 is rapidly phosphorylated after BCR signal transduction, and is believed to downregulate B-cell activation. In this study, we did not detect CD22 phosphorylation in activated B cells after CD38 or CD40 cross-linking, even though CD22 was clearly phosphorylated in the BCR-stimulated B cells. Consistent with this, we found no evidence of physical association between CD38 or CD40 and CD22 in B cells. The lack of association or phosphorylation of CD22 induced by CD38 and CD40 cross-linking indicates that CD22 may not downregulate the activation induced by these two molecules.