Induction of autoimmune disease in CTLA-4^−/−mice depends on a specific CD28 motif that is required forin vivocostimulation

Abstract

CTLA-4-deficient mice develop a lethal autoimmune lymphoproliferative disorder that is strictly dependent on in vivo CD28 costimulation. Nevertheless, it is not known whether there is a specific site on the CD28 molecule that is required for induction of autoimmunity. Using CTLA-4-deficient mice expressing CD28 molecules with various point mutations in the CD28 cytosolic tail, the present study documents that in vivo costimulation for induction of autoimmune disease strictly requires an intact C-terminal proline motif that promotes lymphocyte-specific protein tyrosine kinase Lck binding to the CD28 cytosolic tail, because point mutations in C-terminal proline residues (Pro-187 and Pro-190) completely prevented disease induction. In contrast, in vivo costimulation for disease induction did not require either an intact YMNM motif or an intact N-terminal proline motif, which, respectively, promote phosphoinositide 3-kinase and IL2-inducible T cell kinase binding to the CD28 cytosolic tail. Thus, in vivo CD28 costimulation for induction of autoimmune disease is strictly and specifically dependent on an intact C-terminal proline motif that serves as a lymphocyte-specific protein tyrosine Lck kinase binding site in the CD28 cytosolic tail.

EFIS Lecture: Understanding the CTLA-4 checkpoint in the maintenance of immune homeostasis

“…The proliferation of Treg is known to be positively regulated by CD28 signaling [44,45] suggesting a model in which CTLA--4 regulates Treg proliferation by controlling access of CD28 to their shared ligands (CD80 and CD86). This fits with clear evidence that the biological role of CTLA--4 is regulate the CD28 pathway: accordingly mice that lack CTLA--4 but also lack CD28 [43], or CD80/86 [42], do not exhibit any signs of immune hyperactivation. Likewise, experimental blockade of CD80 and CD86 with a CTLA--4--Ig fusion protein or anti--CD80 and anti--CD86 antibodies also abrogates disease in CTLA--4--deficient mice [37,79].…”

Targeting the PD1/PD-L1 axis in melanoma: Biological rationale, clinical challenges and opportunities

“…In experimental models, mice rapidly develop lymphoproliferative disease with multiorgan lymphocytic infiltration and tissue destruction, including particularly severe myocarditis and pancreatitis, and die at 3-4 weeks of age [28]. The severe phenotype of mice lacking CTLA-4 implies a critical role for CTLA-4 in down-regulating T cell activation and maintaining immunologic homeostasis.…”

CTLA-4 controls follicular helper T-cell differentiation by regulating the strength of CD28 engagement

“…Because the phenotype of CTLA-4 −/− mice is likely due to excessive CD28 engagement (20,21), we hypothesized that the GC response should also be influenced by directly affecting levels of CD28 on T cells. To probe whether changing the amount of CD28 engagement on Tconv altered their ability to support GC formation, we performed adoptive transfer experiments comparing CD28…”