Immune dysregulation caused by homozygous mutations in CBLB
Erin Janssen, … , Aida M. Bertoli-Avella, Raif S. Geha
Erin Janssen, … , Aida M. Bertoli-Avella, Raif S. Geha
Published August 25, 2022
Citation Information: J Clin Invest. 2022;132(20):e154487. https://doi.org/10.1172/JCI154487.
View: Text | PDF
Concise Communication Immunology

Immune dysregulation caused by homozygous mutations in CBLB

Abstract

CBL-B is an E3 ubiquitin ligase that ubiquitinates proteins downstream of immune receptors to downregulate positive signaling cascades. Distinct homozygous mutations in CBLB were identified in 3 unrelated children with early-onset autoimmunity, one of whom also had chronic urticaria. Patient T cells exhibited hyperproliferation in response to anti-CD3 cross-linking. One of the mutations, p.R496X, abolished CBL-B expression, and a second mutation, p.C464W, resulted in preserved CBL-B expression. The third mutation, p.H285L in the SH2 domain of CBL-B, was expressed at half the normal level in the patient’s cells. Mice homozygous for the CBL-B p.H257L mutation, which corresponds to the patient’s p.H285L mutation, had T and B cell hyperproliferation in response to antigen receptor cross-linking. CblbH257L mice had increased percentages of T regulatory cells (Tregs) that had normal in vitro suppressive function. However, T effector cells from the patient with the p.H285L mutation and CblbH257L mice were resistant to suppression by WT Tregs. Bone marrow–derived mast cells from CblbH257L mice were hyperactivated after FcεRI cross-linking, and CblbH257L mice demonstrated exaggerated IgE-mediated passive anaphylaxis. This study establishes CBL-B deficiency as a cause of immune dysregulation.

Authors

Erin Janssen, Zachary Peters, Mohammed F. Alosaimi, Emma Smith, Elena Milin, Kelsey Stafstrom, Jacqueline G. Wallace, Craig D. Platt, Janet Chou, Yasmeen S. El Ansari, Tariq Al Farsi, Najim Ameziane, Ruslan Al-Ali, Maria Calvo, Maria Eugenia Rocha, Peter Bauer, Nouriya Abbas Al-Sannaa, Nashat Faud Al Sukaiti, Abdullah A. Alangari, Aida M. Bertoli-Avella, Raif S. Geha

×

Figure 2

CblbH257L T cells hyperproliferate in response to anti-CD3 and are resistant to Treg suppression.

Options: View larger image (or click on image) Download as PowerPoint
CblbH257L T cells hyperproliferate in response to anti-CD3 and are resi...
(A) Representative immunoblots of CBL-B and GAPDH expression in titrated T cell lysates (left). Densitometry of CBL-B bands normalized to GAPDH (right). (B and C) Numbers of splenocytes and CD3+ splenic T cells (B) and percentages of T cell subsets (C) in 8- to 10-week-old mice (n = 6 mice/group). (D) T cell proliferation (left) in response to anti-CD3, anti-CD3 plus anti-CD28 (middle), and IL-2 secretion (right) in response to anti-CD3. n = 3–6 mice/group. (E) T cells were activated with anti-CD3 for 2 and 20 minutes. Immunoblots for phospho-LAT, phospho-PLCγ1, and GAPDH. (F) T cells were stimulated with CD3 cross-linking followed by ionomycin. Calcium flux was measured by Fluo-4. One representative experiment out of 6 is shown. (G) T cells were stimulated with anti-CD3 for 0–30 minutes and phospho-ERK and phospho-AKT levels were determined by flow cytometry. (H) Percentages of Tregs in the spleen. (I) Suppression of proliferation of CD4+CD25– WT Teffs by WT and CblbH257L Tregs (left). Suppression of CblbH257L and WT Teff proliferation by WT Tregs (right). One experiment out of 3 is shown for A, D, and G and out of 2 for B, C, H, and I. Data in A–D and G–I are presented as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001 by unpaired, 2-tailed Student’s t test.