back in Immune episode 21 you covered a paper by Ahmed et al. (https://pubmed.ncbi.nlm.nih.gov/31150624/) describing an intriguing novel lymphocyte expressing both a BCR and a TCR, which the authors named a dual-expresser (DE) cell. The paper showed that DE cells, although rare, were more frequently found in type 1 diabetes (T1D) patients than in healthy controls and seemed to carry a public BCR that was shared between individuals (x-clonotype). Additionally, the authors claimed that the CDR3 sequence of the x-clonotype encoded a potent T cell auto-antigen when bound to the DQ8 HLA class II allele.
As you mentioned in the episode, these findings, if correct, would implicate DE cells and their x-clonotype in the pathogenesis of T1D and open several opportunities for the diagnosis and treatment of this incurable autoimmune disease.
We set out to replicate two of their major findings: 1) the increased frequency of DE cells in the blood and 2) the presence of the public x-clonotype in T1D patients.
Using a flow cytometry panel identical to the one used by Ahmed et al., (and running samples at two independent institutions by blinded investigators) we were unable to replicate the increased frequency of DE cells in the blood of T1D patients. Additionally, we did not find enrichment of these cells in lymphoid tissues, such as pancreatic lymph nodes and spleen.
We searched for the sequence of the x-clonotype in B cells from 92 individuals (40 T1D and 52 controls, amounting to approx. 1.6 million clonotypes) and did not find it. Our data was published by Cell as a “Matters Arising” paper (https://pubmed.ncbi.nlm.nih.gov/33545036/) together with a reply written by the authors of the original DE cell paper (https://pubmed.ncbi.nlm.nih.gov/33545037/). In the interest of fairness, I’d like to encourage listeners to read both papers.
A previous paper by Julie Burel published in Cytometry Part A (https://pubmed.ncbi.nlm.nih.gov/32400942/) had already raised concerns about technical difficulties in discerning cell-cell complexes in flow cytometry and single-cell sorting. We did not try to question the existence of a BCR/TCR dual-expressing lymphocyte, because it is impossible to prove without doubt that it does not exist. Instead, we focussed on it’s alleged association with T1D and, unfortunately for T1D patients, were unable to replicate the original findings of Ahmed et al..
Thank you for all the work you put into Immune and the MicrobeTV family of podcasts, I have been listening to them for over 10 years now. They have been stable companions through grad school and postdoc in 2 continents. They are fantastic instruments of scientific communication and critical thinking!
All the best,
Dear esteemed Immune Hosts,
A BBC radio programme covered a recent Nature paper – “Gut-educated IgA plasma cells defend the meningeal venous sinuses” by Fitzpatrick et al. It looks important, given the role of IgA in the brain was not appreciated, and might be worth covering on a future programme.
Many thanks for all the episodes and please keep podcasting!
I am a lymphatic cancer survivor 2 years now.
I had a right anterior hemiglossectomy and a right cervical dissection with removal of 33 lymphnodes and 3 were positive for metastasis.
Also, I survived Botulina toxicity 5 years ago.
My question is with my given history is it safe for me to continue to donate blood? I have not given since I had Botulina toxicity.
Dear Immune team and Twiv team.
I am very impressed by hearing the exciting discussion in the Immune episode #36.
I felt that the results showing the absence of Tfh from lymph nodes of severe COVID-19 patients might be important in several ways. Germinal center (GC) is an important architecture for affinity maturation and class switching of antibodies. In the germinal center, B cell clones rapidly proliferate in the dark zone and produce somatic hypermutation of antigen binding sites. Only high affinity B cells are allowed to survive in the light zone of GC with interaction with Tfh and follicular dendritic cells (FDC). I am wondering whether SARS-CoV-2 could infect FDC, which are epithelial origin, and then the formation of GC structure is hampered.
Another point resides in the initial activation of naive T cells by dendritic cells (DC) in T cell area in the context of MHC class II and antigenic peptides. If the initial activation is not strong enough, T cells can express an insufficient level of Bcl-6. This leads to the lack of CXCR5 expression, which is the receptor for CXCL13. Such T cells may stay in the T cell area and may be involved in the extra follicular B cell differentiation. Such B cells are believed to be short-lived, low affinity due to the lack of selection process in the GC and stay in the lymph nodes.
Third, if I remember correctly, the expression of Bcl-6 inhibits differentiation of activated T cells into other T cell subsets, including Th1, Th2 and Th17. Because Th1 cells also produce TNF, the blockade of Tfh pathway could result in the overproduction of TNF from Th1 cells. Vaccines that can create GC, unlike natural infection, may be good ones.
Yasuyuki Imai, PhD.
University of Shizuoka School of Pharmaceutical Sciences