Cytolytic T cell granules. Isolation, structural, biochemical, and functional characterization.

Area of Science:

• Immunology
• Cell Biology

Background:

• Cytoplasmic dense granules in T cells are crucial for immune responses.
• Understanding the molecular mechanisms of T cell-mediated cytotoxicity is essential.

Purpose of the Study:

• To analyze the functional and biochemical properties of isolated cytoplasmic dense granules from cloned T cell lines.
• To identify the proteins responsible for cytolytic activity and their polymerization into poly perforins.

Main Methods:

• Isolation and biochemical analysis of dense granules.
• Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis for protein identification.
• Immunofluorescence and Percoll gradient fractionation for cellular localization.
• Detergent extraction and gel filtration for poly perforin isolation.

Main Results:

• Isolated granules exhibited potent tumoricidal and hemolytic activity.
• Granules contained unique cytolytic proteins (K1-K6) and formed tubular complexes (poly P1, poly P2).
• Poly perforin 1 (poly P1) formation was Ca-dependent and involved disulfide-linked subunits.

Conclusions:

• Dense granules of cytolytic T cells contain proteins that polymerize into poly perforins.
• Poly perforins may cause cytolysis through membrane insertion and transmembrane channel formation.
• Cytolytic granules are specific to cytolytic T cell lineages.