N-Glycosylation in Chronic Lymphocytic Leukemia See article p. 743

Infection Induces Expansion of BIRC5+ Myeloid Cells See article p. 836

TIPE1 Dampens Harmful Effects of TNF-α in Colitis See article p. 874

IFN-γ Signaling Inhibits Treg Function in allo-HCT See article p. 885

IL-27 Treatment Induces M1 Macrophages in Tumors See article p. 895

Chronic lymphocytic leukemia (CLL) patient subsets are distinguished both clinically and genomically. In this Top Read, Iatrou et al. (p. 743) focused on CLL subset #201 to better understand the structural and functional effects of one of its distinguishing genetic features–somatic hypermutation (SHM) in an IGHV gene that affects N-glycosylation sites. Next-generation sequencing analysis of CLL #201 subset patients compared with subset #4 revealed that SHM of #201 BCR Ig genes disrupts or creates more N-glycosylation sites within the H, the L, or both H and L chains. This observation was confirmed by mobility shift assays of PNGase-treated recombinant authentic (A) versus germline revertant (R) CLL #201 mAbs. CLL cell- and human tissue–binding assays of #201 A- versus R-rmAbs pointed to loss or gain of particular H and L chain N-glycosylation sites. Similar trends were observed in reactivity of A- versus R-rmAbs against a subset of viral and bacterial Ags. Together, the data suggest important functional and clinical relevance for the tendency of CLL subset #201 toward recurrent SHM in BCR Ig genes.

In this Top Read, Zhai et al. (p. 885) demonstrate that IFN-γ signaling inhibits regulatory T cell (Treg) expansion and conversion following allogeneic hematopoietic cell transplant (allo-HCT). Mice receiving allo-HCT from IFN-γ receptor knockout (GRKO) mice had significantly increased numbers of Tregs at days 12 and 25, compared with those receiving WT allo-HCT. Recipients of GRKO T cells showed an expansion of Tregs and an increase in conversion of Tregs from conventional T cells, which resulted in an attenuated graft-versus-host disease (GVHD) response compared with mice receiving WT allo-HCT. Deleting the pre-existing Treg population prior to GRKO allo-HCT induced early GVHD but maintained the graft-versus-leukemia effects without progressing to severe GVHD. These findings were replicated in human culture systems ex vivo and in a humanized mouse model, suggesting that inhibition of IFN-γ signaling could be a potential therapeutic target for transplant patients. Together, these data provide evidence that IFN-γ signaling inhibits Treg expansion and conversion following allo-HCT.

In this Top Read, Loredan et al. (p. 836) show that CX3CR1+BIRC5+ myeloid cells expand in mice infected with either Schistosoma mansoni or Staphylococcus aureus. BIRC5+ cells from both infections and a previously published atherosclerosis model revealed that all BIRC5+ cells shared a common transcriptional pattern, with increased expression of Ki67 and Stmn1, indicating a proclivity for proliferation. In S. aureus infections, the expansion of CX3CR1+BIRC5+ myeloid cells was dependent on the bacterial virulence factor, leucocidin. Deleting Birc5 in CX3CR1+ myeloid cells prior to S. aureus infection resulted in increased survival, decreased bacterial burden, and altered systemic cytokine expression. These data demonstrate that CX3CR1+BIRC5+ cells can expand based on their microenvironment and that they play a pathogenic role in S. aureus infections.

In this Top Read, Zhu et al. (p. 895) investigated the role of IL-27 in myeloid lineage cells. First, the authors demonstrated that administration of IL-27 producing adeno-associated virus (AAV-IL-27) increased frequencies of LinSca1+c-Kit+ stem cells and LinSca1+c-Kit+CD16+CD34+ granulocyte-monocyte progenitor cells in bone marrow, which was followed by expansion of CD11b+Gr1+ cells that was IL-27R and Stat3 dependent, but was inhibited by Stat1 signaling. CD11b+Gr1+ cells isolated from spleen or bone marrow of AAV-IL-27–treated mice were T cell suppressive in vitro but did not promote tumor growth in vivo. Together, the data indicate that IL-27–mediated activation of Stat3 induces expansion of CD11b+Gr1+ cells via hematopoietic stem cell accumulation in the bone marrow, leading to tumor suppression and accumulation of MHC class I/II+ M1 macrophages in the tumor microenvironment.

In this Top Read, Lou et al. (p. 874) report that TIPE1, a member of the TNFα-induced protein 8 family, is critical for intestinal epithelial cell (IEC) barrier integrity and homeostasis in a mouse model of colitis. Whereas Tipe1 knockout mice, like previously reported Tipe knockouts, were born relatively healthy, they were hypersensitive toward dextran sulfate sodium–induced colitis, having higher mortality and more severe intestinal abnormalities. Loss of Tipe1 correlated with increased expression of inflammatory mediators, such as Il1b, Il6, and Mcp1, decreased expression of tight junction genes, increased infiltration of immune cells to the colon, and increased IEC death. Double knockout mice lacking Tipe1 and Tnfr1 developed less severe colitis symptoms. Interestingly, despite previous hypotheses linking TIPE1 to development of colorectal cancer, Tipe1 knockout mice did not show increased incidence of colorectal cancer or sporadic intestinal tissue tumors. Finally, Tipe−/−Tipe1−/− double knockout mice were the most severely impacted with regard to mortality, immune, and physiological phenotypes, suggesting that TIPE and TIPE1 play at least partially redundant roles in maintaining intestinal homeostasis.