Early specific antibody responses against SARS-CoV-2 include IgG, IgM, and IgA, but IgA may neutralize virus and control infection to a larger extent.

IgA influences bacterial fitness in the intestinal lumen and is only partially compensated for by IgM in selective IgA-deficient patients.

Significance: CD4 ⁺ regulatory T (Treg) cells expressing CD25 and the transcription factor forkhead box P3 (FOXP3) play indispensable roles for immunological self-tolerance and homeostasis. Because human FOXP3 ⁺ CD25 ⁺ CD4 ⁺ T cells are heterogeneous in function and differentiation status, their analysis and manipulation for treating immunological diseases remains a challenge. Here we show that CD15s (sialyl Lewis x) is specifically expressed by activated, terminally differentiated, and most suppressive FOXP3 ^high Treg cells, allowing their separation from nonsuppressive FOXP3 ⁺ CD4 ⁺ T cells secreting inflammatory cytokines. Removal of CD15s ⁺ CD4 ⁺ T cells from human blood is indeed sufficient to enhance in vitro antitumor and antiviral antigen responses. CD15s is therefore useful for phenotypic as well as functional analysis of human Treg subpopulations and for targeting them to control immune responses.

Background: Plasmodium falciparum immature gametocytes accumulate in the bone marrow, but their exact location in this tissue remains unclear. Methods: The stage and deposition pattern of gametocytes was analysed on histological sections of a bone marrow sample collected in a patient with subacute P. falciparum malaria. Results: A majority (89%) of immature stages II to IV gametocytes and a minority (29%) of mature stage V gametocytes were observed in extravascular spaces. Discussion and conclusion: These observations represent a valuable step towards understanding sequestration patterns of P. falciparum gametocytes and may ultimately lead to novel transmission-blocking interventions.