Trigger-happy resident memory CD4+ T cells inhabit the human lungs.

Resident memory T cells (TRM) reside in the lung epithelium and mediate protective immunity against respiratory pathogens. Although lung CD8+ TRM have been extensively characterized, the properties of CD4+ TRM remain unclear. Here we determined the transcriptional signature of CD4+ TRM, identified by the expression of CD103, retrieved from human lung resection material. Various tissue homing molecules were specifically upregulated on CD4+ TRM, whereas expression of tissue egress and lymph node homing molecules were low. CD103+ TRM expressed low levels of T-bet, only a small portion expressed Eomesodermin (Eomes), and although the mRNA levels for Hobit were increased, protein expression was absent. On the other hand, the CD103+ TRM showed a Notch signature. CD4+CD103+ TRM constitutively expressed high transcript levels of numerous cytotoxic mediators that was functionally reflected by a fast recall response, magnitude of cytokine production, and a high degree of polyfunctionality. Interestingly, the superior cytokine production appears to be because of an accessible interferon-γ (IFNγ) locus and was partially because of rapid translation of preformed mRNA. Our studies provide a molecular understanding of the maintenance and potential function of CD4+ TRM in the human lung. Understanding the specific properties of CD4+ TRM is required to rationally improve vaccine design.

Enhanced uptake of blood coagulation factor VIII containing immune complexes by antigen presenting cells.

Essentials Anti-factor (F) VIII antibody formation is a major complication in the treatment of hemophilia A. We investigated uptake of FVIII and FVIII immune complex by bone marrow derived dendritic cells. Immune complex formation increased uptake of FVIII 3-4 fold in a Fcγ receptor dependent manner. FVIII immune complex binding to Fcγ receptors may modulate immune tolerance induction. SUMMARY: Background A major complication in the treatment of hemophilia A is the development of inhibitory antibodies targeting coagulation factor VIII (FVIII). Eradication of these inhibitors can be established by immune tolerance induction (ITI), which consists of daily administration of high dosages of FVIII. FVIII immune complexes (FVIII-IC) could be formed following FVIII infusion in patients with pre-existing anti-FVIII antibodies. Objectives Here we studied endocytosis of FVIII-IC by bone marrow-derived dendritic cells (BMDCs). Methods BMDCs were pulsed with FVIII/FVIII-IC and uptake was assessed by flow cytometry and confocal imaging. Results BMDCs were able to efficiently internalize FVIII-IC in a dose-dependent manner, 3-4-fold more efficiently when compared with equimolar concentrations of non-complexed FVIII. Uptake of FVIII-IC, but not FVIII alone, could be inhibited with anti-Fcγ receptor (FcγR) antibody 2.4G2, indicating functional involvement of FcγR. No internalization of FVIII-IC was observed in BMDCs lacking FcγRI, FcγRIIb, FcγRIII and FcγRIV. Genetic ablation of FcγRIIb, FcγRIII or FcγRIV individually did not affect the ability of anti-FVIII IgG to promote the uptake of FVIII. BMDCs lacking FcγRI showed lower FVIII-IC uptake levels when compared with other single FcγR null BMDCs. Expression of the inhibitory FcγRIIb alone was sufficient to internalize FVIII-IC more efficiently than FVIII. Conclusions FcγR are critical in the internalization of FVIII-IC by BMDCs and multiple FcγR can contribute independently to this process. Our findings provide a basis for future studies to address whether the outcome of ITI is dependent on the interplay between FVIII-IC and inhibitory and activating FcγR.

Enhanced costimulation by CD70+ B cells aggravates experimental autoimmune encephalomyelitis in autoimmune mice.

OBJECTIVE: Assess whether CD70+ B cells contribute to EAE. MATERIALS AND METHODS: MOG-specific TCR transgenic mice (2D2) were crossed with mice with constitutive CD70 expression on B cells. The development of EAE and the phenotype of B-T lymphocytes were studied in 2D2xCD70 animals. RESULTS: Spontaneous EAE developed in 20% of 2D2xCD70 and 3% of 2D2 mice. EAE was also more severe in 2D2xCD70 versus 2D2 animals upon MOG immunization. The susceptibility of 2D2xCD70 to EAE was associated with fewer FoxP3+ T cells. CONCLUSIONS: Expression of CD70 by B cells aggravates EAE possibly by reducing the number of regulatory T cells.

Isolation of the intact white pulp. Quantitative and qualitative analysis of the cellular composition of the splenic compartments.

The spleen is anatomically and functionally divided into two compartments: the red pulp, where particles are effectively removed from the blood, and the white pulp, where specific immune responses are generated. Here the isolation of white pulp from red pulp is described, allowing a detailed analysis of the cellular components of both red and white pulp separately. A striking abundance of memory T cells was found in the white and red pulp with an overall ratio of T and B cells in the white pulp being similar to that in lymph nodes. Both NK and gamma delta T cells can be found in white pulp and lymph nodes, but granulocytes are absent. The distribution of dendritic cell subsets showed significant differences between white pulp and lymph nodes. Furthermore, short-term homing experiments showed that migration of lymphocytes into the white pulp greatly exceeded that into lymph nodes, with significant differences in migration of various lymphocytes subsets. This suggests a different migration and retention mechanism in the white pulp. This new isolation technique will allow further analysis of the functional capacities of the splenic compartments.

Protein C inhibitor may modulate human sperm-oocyte interactions.

Protein C inhibitor (PCI) is a heparin-binding plasma serine protease inhibitor that was originally identified as an inhibitor of activated protein C. PCI has a broad protease specificity, inhibiting several proteases in hemostasis and fibrinolysis by acting as a suicide substrate. Recently it has been reported that proteases of the reproductive system, such as acrosin, prostate-specific antigen, and tissue kallikrein, can also be effectively inhibited by PCI. However, a direct relation between PCI and physiological events during fertilization has not yet been established. An attempt was made to monitor and localize the inhibition of the sperm protease acrosin by PCI. Localization experiments for PCI on epididymal spermatozoa showed that PCI is present on the acrosomal cap of human spermatozoa, which demonstrates the early presence of PCI in the male reproductive tract. Induction of the acrosome reaction in ejaculated human spermatozoa resulted in the disappearance of PCI from the plasma membrane overlying the acrosomal head and the appearance of a strict distribution at the equatorial segment of human spermatozoa. The activity of acrosin in sperm extracts could be effectively inhibited by PCI. Zona-binding assays showed that active PCI is able to block sperm-egg binding in a concentration-dependent manner. The combination of the potent inhibition of acrosin and sperm-egg binding by PCI and the localization studies suggested that PCI may protect spermatozoa against premature acrosome reaction and degradation, thereby modulating the acrosin activity so that it can coincide with binding to the oocyte.