Randomly inserted TCR alpha transgene construct that combines rearranged genomic DNA of Trav14-1*02 and Traj42*01. The promoter driving the expression is described in PMID:3260351. To uniquely identify the associated DNA, please consult the TRAV and TRAJ pages of the International Immunogenetics (IMGT) Information System.

Randomly inserted TCR beta transgene construct that combines rearranged genomic DNA of Trbv2*1, Trbd1, and Trbj2-5. The promoter driving the expression is described in PMID:7714342.To uniquely identify the associated DNA, please consult the TRBV, TRBD, and TRBJ pages of the International Immunogenetics (IMGT) Information System.

Background
(The line is unpublished at the time of curation, which is why additional detail is provided here)

The T cell receptor (TCR) transgenic mice express TCRs specific to cardiac myosin heavy chain-alpha (Myhc 334-352). This peptide fragment of the whole protein (Myhc) is highly immunogenic in myocarditis-susceptible, A/J mice that express the major histocompatibility complex (MHC) class II molecule (H-2a). Essentially, A/J mice immunized with Myhc 334-352 in complete Freund’s adjuvant (CFA) develop severe myocarditis mediated by CD4 T cells specific to Myhc 334-352. Since the disease features of this model resemble post-infectious myocarditis, for example, as might occur in Coxsackievirus B3 infection, this disease model has been used extensively in the literature.

However, the donor recently discovered that Myhc 334-352 could also bind another MHC class II molecule in C57BL/6 mice that express the MHC class II allele called IAb, albeit poorly. Additionally, C57BL/6 mice develop only mild (if any) myocarditis by immunization with Myhc 334-352 in CFA.

Taken together, immunization with a single peptide (Myhc 334-352) can lead to two different phenotypes, i.e., severe myocarditis in the wild type A/J mice and no myocarditis in wild-type C57BL/6 mice. This offers an excellent framework to determine the immune mechanisms of myocarditis in susceptible (A/J) vs. resistant (C57BL/6) mice. Of note, myocarditis can lead to dilated cardiomyopathy (DCM), and detection of heart infiltrates in association with the dysfunctional cardiac features of DCM is termed inflammatory cardiomyopathy.

Since it has been a significant challenge to determine the functionalities of heart-specific T cells, the donor made efforts to create the TCR transgenic mice for Myhc 334-352. Their creation needed us to inject the TCR alpha, and TCR beta constructs first into the pronuclei of C57BL/6 mice since this mouse strain is commonly employed in the transgenic field and such as system is not available for A/J mice. Under these circumstances, it is a general practice to backcross the pups generated in C57BL/6 mice onto the A/J background for ten generations (MMRRC:69588-69590).

Disease phenotype in myocarditis-resistant C57BL/6 mice.

The donor noted that both CD4 and CD8 T cells from C57BL/6 mice express TCRs as evaluated by transgene expression. This was assessed by PCR analysis and flow cytometry. The donor had used the TCR vbeta4 antibody to confirm the expression of transgene at a protein level. Expectedly, T cells from naïve transgenic mice did not respond to Myhc 334-352, but upon immunization with Myhc 334-352 in CFA, both CD4 and CD8 T cells respond to Myhc 334-352 as evaluated by proliferation assay. These data suggest that in vivo priming with Myhc is needed for T cells to respond. Nonetheless, the response of both CD4 and CD8 T cells to Myhc 334-352 was expected because the donor had previously demonstrated that the Myhc 334-352 encompasses epitopes for both CD4 and CD8 T cells. Based on this observation, the donor proposes that the functionalities of heart-specific, CD4 and CD8 T cells can be investigated within the single transgenic system without having to generate transgenic mice individually for these two subsets of T cells. This is critical because CD4 and CD8 T cells mediate their functions by distinct pathways. While CD4 T cells contribute to tissue damage via cytokine secretion, CD8 T cells induce tissue destruction by cytotoxicity.

Furthermore, while naïve transgenic C57BL/6 mice failed to develop myocarditis spontaneously, animals immunized with Myhc 334-352 in CFA develop only mild myocarditis. Additionally, the transgenic T cells produce mainly interferon-gamma. Studies evaluating whether underproduction of interleukin-17 may contribute to the lack of myocarditis in the C57BL/6 mice are underway.

Overall, until the transgenic mice on myocarditis-susceptible, A/J mice become available, the donor expects that the transgenic mice myocarditis-resistant, C57BL/6 mice can be used as valuable tools to determine the disease-resistance mechanisms of myocarditis, DCM, and inflammatory cardiomyopathy research.

Microinjection of two separate constructs into the pronuclei of C57BL/6J zygotes.

• Cardiovascular
• Immunology and Inflammation
• Models for Human Disease
• Research Tools

Blüthmann H, Kisielow P, Uematsu Y, Malissen M, Krimpenfort P, Berns A, von Boehmer H, Steinmetz M. T-cell-specific deletion of T-cell receptor transgenes allows functional rearrangement of endogenous alpha- and beta-genes. Nature. 1988 Jul 14;334(6178):156-9. doi: 10.1038/334156a0. (Medline PMID: 3260351)

Kouskoff V, Signorelli K, Benoist C, Mathis D. Cassette vectors directing expression of T cell receptor genes in transgenic mice. J Immunol Methods. 1995 Mar 27;180(2):273-80. doi: 10.1016/0022-1759(95)00002-r. (Medline PMID: 7714342)