Unusual expression of CD2 in sheep: implications for T cell interactions

Area of Science:

• Immunology
• Cell Biology
• Comparative Mammalian Studies

Background:

• The CD2 molecule is a key adhesion and activation molecule on mammalian T lymphocytes, binding to the LFA-3 receptor.
• Species-specific differences in immune cell surface molecule expression can significantly impact immune responses.

Purpose of the Study:

• To investigate and compare the expression patterns of the CD2 molecule on T lymphocytes in sheep versus humans.
• To explore the functional implications of differential CD2 expression on sheep T cell subsets, particularly gamma/delta T cells.

Main Methods:

• Flow cytometry using monoclonal antibodies (including T19) to identify and quantify T cell subsets.
• Analysis of CD2 expression on peripheral T cells and thymocytes in sheep of different ages.
• Functional assays to assess T cell adhesion to dendritic cells and cytotoxic T lymphocyte (CTL) activity.

Main Results:

• Sheep T cells exhibit significantly different CD2 expression compared to humans, with weak expression on peripheral T cells and thymocytes.
• A large subset of sheep T cells (T19+), identified as gamma/delta T cells, completely lacks CD2 expression.
• CD2 expression is critical for T cell adhesion to dendritic cells, but not essential for CTL-mediated killing by T19+ cells.

Conclusions:

• Differential expression of CD2 and LFA-3 between sheep and humans highlights species-specific variations in T cell regulation.
• The absence of CD2 on a major sheep T cell subset (T19+) influences cell adhesion and potentially other immune functions.
• These findings underscore the importance of considering interspecies differences in immune molecule expression for understanding T cell biology.