Severity of SARS-CoV-2 infection is linked to double-negative (CD27- IgD-) B cell subset numbers.

OBJECTIVES: The role of B cells in COVID-19, beyond the production of specific antibodies against SARS-CoV-2, is still not well understood. Here, we describe the novel landscape of circulating double-negative (DN) CD27- IgD- B cells in COVID-19 patients, representing a group of atypical and neglected subpopulations of this cell lineage. METHODS: Using multiparametric flow cytometry, we determined DN B cell subset amounts from 91 COVID-19 patients, correlated those with cytokines, clinical and laboratory parameters, and segregated them by principal components analysis. RESULTS: We detected significant increments in the DN2 and DN3 B cell subsets, while we found a relevant decrease in the DN1 B cell subpopulation, according to disease severity and patient outcomes. These DN cell numbers also appeared to correlate with pro- or anti-inflammatory signatures, respectively, and contributed to the segregation of the patients into disease severity groups. CONCLUSION: This study provides insights into DN B cell subsets' potential role in immune responses against SARS-CoV-2, particularly linked to the severity of COVID-19.

Altered distribution of peripheral blood memory B cells in humans chronically infected with Trypanosoma cruzi.

Numerous abnormalities of the peripheral blood T cell compartment have been reported in human chronic Trypanosoma cruzi infection and related to prolonged antigenic stimulation by persisting parasites. Herein, we measured circulating lymphocytes of various phenotypes based on the differential expression of CD19, CD4, CD27, CD10, IgD, IgM, IgG and CD138 in a total of 48 T. cruzi-infected individuals and 24 healthy controls. Infected individuals had decreased frequencies of CD19+CD27+ cells, which positively correlated with the frequencies of CD4+CD27+ cells. The contraction of CD19+CD27+ cells was comprised of IgG+IgD-, IgM+IgD- and isotype switched IgM-IgD- memory B cells, CD19+CD10+CD27+ B cell precursors and terminally differentiated CD19+CD27+CD138+ plasma cells. Conversely, infected individuals had increased proportions of CD19+IgG+CD27-IgD- memory and CD19+IgM+CD27-IgD+ transitional/naïve B cells. These observations prompted us to assess soluble CD27, a molecule generated by the cleavage of membrane-bound CD27 and used to monitor systemic immune activation. Elevated levels of serum soluble CD27 were observed in infected individuals with Chagas cardiomyopathy, indicating its potentiality as an immunological marker for disease progression in endemic areas. In conclusion, our results demonstrate that chronic T. cruzi infection alters the distribution of various peripheral blood B cell subsets, probably related to the CD4+ T cell deregulation process provoked by the parasite in humans.

Inmunoglobulina D: propiedades y relevancia clínica / Nonmyeloablative transplantation of haematopoietic cells

La inmunoglobulina D (IgD) es, de las proteínas presentes en el suero humano, la menos conocida en cuanto a su función biológica. En la actualidad, se han incrementado los estudios de la IgD sérica en relación con diferentes enfermedades, al demostrarse su participación en determinados trastornos febriles en niños, así como el papel de esta en la respuesta inmune, dado por su expresión en la membrana de los linfocitos B formando parte del receptor antigénico. En nuestro trabajo se revisan las propiedades de la IgD y su papel en la respuesta inmune, así como su relación con diferentes enfermedades(AU)

Hyperimmunoglobulinemia D and periodic fever syndrome (HIDS) in a child with normal serum IgD, but increased serum IgA concentration.

This report describes a boy with hyperimmunoglobulinemia D and periodic fever syndrome (HIDS). The serum IgD level was normal, but the serum IgA concentration was markedly elevated. In addition, he had a history of orchitis on two occasions, a previously unreported manifestation of HIDS. This report expands the clinical and laboratory features associated with HIDS and serves to emphasize that a normal serum IgD level does not exclude the diagnosis of HIDS.

Periodic fever, aphthous stomatitis, pharyngitis, and adenopathy syndrome: clinical characteristics and outcome.

We report 28 patients (20 male) with a syndrome characterized by abrupt onset of fever, malaise, aphthous stomatitis, tonsillitis, pharyngitis, and cervical adenopathy (PFAPA syndrome). Episodes of fever occurred at intervals of 5.1 +/- 1.3 weeks beginning at the age of 4.2 +/- 2.7 years. Fever, malaise, tonsillitis with negative throat cultures, and cervical adenopathy were reported in all 28 patients, aphthae in 19, headache in 5, abdominal pain in 5, and arthralgia in 3. Mild hepatosplenomegaly was observed in 6 patients. Mild leukocytosis, elevation of the erythrocyte sedimentation rate, and fibrinogen were found during attacks. These episodes of illness resolved spontaneously in 4.3 +/- 1.7 days. Serum IgD was found elevated (>100 U/mL) in 12 of the 18 patients tested (140.2 +/- 62.4 U/mL). Affected children grow normally, have no associated diseases, and have no long-term sequelae. Attacks were aborted by a single dose of oral prednisone (2 mg/kg) at the beginning of the attack in all 15 patients in whom this medication was prescribed. In 9 patients the syndrome has completely resolved (beginning at the age of 2.9 +/- 1.3 and lasting 8 +/- 2.5 years). In 3 other patients complete resolution of the attacks occurred after tonsillectomy was performed. PFAPA is sporadic, and no ethnic predilection was found. Increased awareness of the clinical syndrome has resulted in more frequent diagnosis and adequate treatment.