The Related Adaptors, Adaptor in Lymphocytes of Unknown Function X and Rlk/Itk-Binding Protein, Have Nonredundant Functions in Lymphocytes

Abstract

Adaptors play a critical role in regulating signaling pathways that control lymphocyte development and activation. Adaptor in lymphocytes of unknown function X (ALX) and Rlk/Itk-binding protein (RIBP) are adaptors related by structure and sequence, coexpressed in T cells. Mice deficient for each adaptor demonstrated that ALX and RIBP, respectively, negatively and positively regulate T cell activation in response to TCR/CD28 stimulation. However, these results did not preclude that they may function redundantly in other cell populations, or in response to other stimuli. Therefore, to understand the relationship between these related adaptors, ALX/RIBP-deficient mice were generated. We demonstrate that although ALX and RIBP are expressed throughout T cell development, T cell development occurs normally in these mice. Using the H-Y TCR transgenic model, positive and negative selection were found to proceed unimpeded in the absence of ALX and RIBP. We demonstrate that RIBP is also expressed in B cells; however, RIBP- and ALX/RIBP-deficient mice had normal B cell development, and responded equivalently to wild type in response to IgM, CD40, B cell-activating factor/B lymphocyte stimulator, CpG, and LPS. Interestingly, T cells deficient in both ALX and RIBP behaved similarly to those deficient in ALX alone during T cell activation in response to TCR/CD28, exhibiting increased IL-2 production, CD25 expression, and proliferation, thus showing that ALX deficiency masked the effect of RIBP deficiency. ALX/RIBP-deficient T cells did not have any alterations in either activation-induced cell death or Th1/2 polarization. Therefore, we did not find any functional redundancy or synergy during lymphocyte development, selection, activation, or survival in ALX/RIBP-deficient mice, demonstrating that these molecules function independently.

SH2D2A Modulates T Cell Mediated Protection to a B Cell Derived Tumor in Transgenic Mice

“…While Drappa and colleagues reported that injection of superantigen did not lead to deletion of the targeted T cells in SH2D2A -deficient mice [13], this was not confirmed by another group [12]. In a classic model of negative selection in the thymus, SH2D2A -deficient H-Y TCR-transgenic male mice displayed increased numbers of both DP and SP CD4+ and CD8+ thymocytes compared normal mice [12], suggesting that negative selection in the absence of SH2D2A is not as efficient as in wild type mice. In the normal situation, clonal deletion in the thymus occurs late in development, at the DP-to-SP transition [35].…”

“…Despite its presumed role in regulating Lck and Itk during T cell signaling, SH2D2A -deficient mice develop normally and have a normal distribution of double negative (DN), double positive (DP) and single positive (SP) thymocytes [11], [12]. However, when stimulated with soluble anti-CD3 or anti-CD3/CD28 antibodies, peripheral T cells from SH2D2A -deficient mice proliferate less vigorously compared to cells from control mice [11].…”

NKAP Is a Transcriptional Repressor of Notch Signaling and Is Required for T Cell Development

“…Increases in Notch target gene expression were also observed in the CD4 SP and CD8 SP populations as well (all but Dtx1 expression in CD8 SP T cells were statistically significant with at least p<0.01). RIBP expression, which remains constant throughout T cell development was examined as a control (Perchonock et al, 2007). Deletion of NKAP did not alter RIBP expression in DP, CD4 SP or CD8 SP populations, demonstrating that loss of NKAP does not generally increase transcription.…”

WASH Knockout T Cells Demonstrate Defective Receptor Trafficking, Proliferation, and Effector Function

“…Analysis of thymocyte development and T cell subpopulations were performed as previously described (24). Briefly, thymocyte single-cell suspensions were generated using 100-m-pore-size nylon mesh filters (BD Biosciences) and surface stained with the following reagents: fluorescein isothiocyanate (FITC)-CD8, TCR␤, TCR␥␦, CD3ε, B220, CD19, CD11c, DX5, NK1.1, Ter119, Mac1 (BD Pharmingen), phycoerythrin (PE)-TCR␤, CD8, CD3ε PerCP-CD4, allophycocyanin (APC)-CD8, CD25, and APC-Cy7-c-kit (eBioscience).…”