Hyaluronan induces cell death in activated T cells through CD44

Area of Science:

• Immunology
• Cell Biology
• Extracellular Matrix Biology

Background:

• Leukocyte activation involves CD44 binding to hyaluronan, an extracellular matrix component.
• CD44's role in T cell activation-induced cell death (AICD) and its interaction with hyaluronan require further investigation.

Purpose of the Study:

• To investigate the consequences of hyaluronan binding by CD44 in T cells using gain and loss of function mutants.
• To elucidate the mechanism of hyaluronan-induced T cell death.

Main Methods:

• Utilized CD44 mutants with altered hyaluronan-binding capabilities in Jurkat T cells.
• Examined T cell susceptibility to activation-induced cell death under varying hyaluronan concentrations and molecular masses.
• Assessed hyaluronan-induced cell death in splenic T cells, including Fas-deficient conditions.

Main Results:

• CD44 mutants preventing chondroitin sulfate addition showed increased hyaluronan binding and susceptibility to AICD.
• A CD44 mutant unable to bind hyaluronan exhibited resistance to cell death.
• Hyaluronan, especially high molecular mass forms, induced rapid, Fas- and caspase-independent cell death in activated T cells.
• A subpopulation of splenic T cells undergoing AICD displayed high hyaluronan binding.

Conclusions:

• Hyaluronan binding to CD44 can induce T cell death through a Fas-independent pathway.
• This mechanism is significant in activated T cells with high hyaluronan-binding capacity.
• The size and amount of hyaluronan influence the extent of T cell death.