ABSTRACT
Exposure to bacterial superantigens, such as staphylococcal enterotoxin B (SEB), can lead to the induction of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). In the current study, we investigated the role of CD44 in ALI/ARDS. Intranasal exposure of CD44 wild-type mice to SEB led to a significant increase in the expression of CD44 on lung mononuclear cells. CD44 knockout mice developed significantly reduced SEB-induced ALI/ARDS, through reduced inflammatory cytokine production and reduced lung inflammatory cells, compared to similarly treated CD44 wild-type mice. Mechanistically, deletion of CD44 altered SEB-induced cytokine production in the lungs and reduced the ability of SEB-exposed leukocytes to bind to lung epithelial cells. Finally, treatment of SEB-exposed mice with anti-CD44 mAbs led to significant reduction in vascular permeability, reduction in cytokine production, and prevented inflammatory cell infiltration in the lungs. Together, these results suggest the possibility of targeting CD44 for the treatment of SEB-induced ALI/ARDS.
Subject(s)
Acute Lung Injury/immunology , Enterotoxins , Hyaluronan Receptors/immunology , Acute Lung Injury/physiopathology , Animals , Antibodies, Monoclonal/immunology , Bronchoalveolar Lavage Fluid/immunology , Capillary Permeability , Cell Adhesion , Cell Line , Cell Proliferation , Cytokines/immunology , Epithelial Cells/physiology , Female , Hyaluronan Receptors/genetics , Leukocytes, Mononuclear/physiology , Mice , Mice, Inbred C57BL , Mice, Knockout , Pneumonia , Spleen/cytologyABSTRACT
In the current study, we examined the potential significance of CD44 expression on lymphokine-activated killer (LAK) cells in their interaction and killing of melanoma cells. Stimulation of splenocytes with IL-2 led to a significant increase in the expression of CD44 on T cells, NK cells, and NKT cells. Treatment of melanoma-bearing CD44 WT mice with IL-2 led to a significant reduction in the local tumor growth while treatment of melanoma-bearing CD44 KO mice with IL-2 was ineffective at controlling tumor growth. Furthermore, the ability of splenocytes from IL-2-treated CD44 KO mice to kill melanoma tumor targets was significantly reduced when compared to the anti-tumor activity of splenocytes from IL-2-treated CD44 WT mice. The importance of CD44 expression on the LAK cells was further confirmed by the observation that adoptively transferred CD44 WT LAK cells were significantly more effective than CD44 KO LAK cells at controlling tumor growth in vivo. Next, the significance of the increased expression of CD44 in tumor killing was examined and showed that following stimulation with IL-2, distinct populations of cells with low (CD44(lo)) or elevated (CD44(hi)) expression of CD44 are generated and that the CD44(hi) cells are responsible for killing of the melanoma cells. The reduced killing activity of the CD44 KO LAK cells did not result from reduced activation or expression of effector molecules but was due, at least in part, to a reduced ability to adhere to B16F10 tumor cells.
