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Murine CD7 shares antigenic cross-reactivity with HSP-60
Brandon A Howard1, Gregory D Sempowski, Richard M Scearce
1Departments of Medicine, Duke University Medical Center, Duke Human Vaccine Institute, Durham, North Carolina, USA.
Insights
Researchers developed rat monoclonal antibodies (MAbs) to mouse CD7 (mCD7). Unexpectedly, these MAbs targeted heat shock protein 60 (HSP-60), suggesting molecular mimicry and leaving the surface expression of mCD7 unresolved.
Area of Science:
- Immunology
- Molecular Biology
Background:
- Human CD7 (hCD7) is an Ig superfamily molecule on T cells and NK cells, with known ligands and a role in endotoxic shock resistance.
- Mouse CD7 (mCD7) protein distribution and specific monoclonal antibodies (MAbs) were previously unknown.
Purpose of the Study:
- To develop rat MAbs against mCD7.
- To investigate the distribution of mCD7 protein in mice.
Main Methods:
- Immunization of rats with recombinant mCD7 protein to generate MAbs.
- Western blot and immunoprecipitation of various mouse tissue extracts.
- Epitope mapping of recognized sites on HSP-60 and recombinant mCD7.
Main Results:
- Three rat MAbs were successfully raised against mCD7.
- These MAbs cross-reacted with murine heat shock protein 60 (HSP-60) in both wild-type and CD7-deficient mice.
- Epitope mapping revealed distinct, non-homologous epitopes on HSP-60 and mCD7.
Conclusions:
- The generated anti-mCD7 MAbs exhibit molecular mimicry with HSP-60.
- The surface expression of mCD7 in mice remains uncertain due to cross-reactivity with HSP-60.
Abstract:
Human (h) CD7 is a 40 kDa single chain Ig superfamily molecule that is expressed on thymocytes, a major subunit of peripheral T cells, and most natural killer cells. Ligands for hCD7 include the epithelial cell-produced molecule, K-12, and galectin. Mice deficient in CD7 have been shown to be resistant to LPS-induced endotoxic shock syndromes. However, monoclonal antibodies (MAb) to mouse (m) CD7 have yet to be produced, nor is the distribution of mCD7 protein in mice known. We have raised a panel of three rat MAbs to mCD7 by immunizing rats with recombinant mCD7 protein. However, using Western blot and immunoprecipitation of tissue extracts from mouse thymus, spleen, liver, brain, lymph node and skin, these anti-mouse CD7 MAbs bound only to murine heat shock protein 60 (HSP-60) present both in wild-type (CD7+/+) and CD7-deficient (CD7-/-) mice. Epitope mapping of the sites on HSP-60 and recombinant mCD7 recognized by mCD7 MAbs demonstrated non-homologous amino acid sequence epitopes recognized by anti-CD7 MAbs on both proteins. These data demonstrated molecular mimicry of mCD7 with HSP-60, and leave open the question of surface expression of mCD7.
