Specific spontaneous cytotoxic activity in human T cell colonies.

Area of Science:

• Immunology
• Cell Biology

Background:

• T cell colonies derived from human peripheral blood leukocytes demonstrate spontaneous cytotoxic activity against various target cells.
• This cytotoxicity is observed even when the blood donor has no prior sensitization to the targets, indicating an innate immune response.
• Tumor cells are disproportionately targeted for destruction by these T cell colonies.

Purpose of the Study:

• To investigate the nature and specificity of effector cells within T cell colonies responsible for spontaneous cytotoxicity.
• To differentiate these effector cells from known immune cells like natural killer (NK) cells and antibody-dependent cellular cytotoxicity (ADCC) mediators.

Main Methods:

• In vitro culture of T cell colonies from normal human peripheral blood leukocytes.
• Assay of cytotoxic activity against diverse target cells.
• Analysis of effector cell surface markers, including sheep erythrocyte receptors and Fc receptors for IgG.

Main Results:

• Colony cells exhibit spontaneous cytotoxicity against non-sensitized target cells, with a preference for tumor cells.
• The cytotoxic activity against two different targets segregated independently across colonies, suggesting specificity restriction of effector cells.
• A significant proportion of effector cells possess receptors for sheep erythrocytes but lack Fc receptors for IgG.
• These characteristics make it unlikely that the effector cells are NK cells or ADCC-mediating cells.

Conclusions:

• The effector cells mediating spontaneous cytotoxicity in T cell colonies are likely cytotoxic T lymphocytes.
• These cells display specificity and target tumor cells preferentially.
• The findings distinguish these cytotoxic T lymphocytes from NK cells and ADCC-mediating cells based on receptor expression and specificity.