Adhesive interaction between peripheral blood mononuclear cells and activated platelets in the presence of anti-human leukocyte antigen Class I alloantibody causes production of IL-1β and IL-8

TLT-1 Promotes Platelet-Monocyte Aggregate Formation to Induce IL-10-Producing B Cells in Tuberculosis

The immunoregulation of platelets and platelet-monocyte aggregates (PMAs) is increasingly recognized, but it roles in tuberculosis (TB) remain to be elucidated. In this study, we found that CD14⁺CD41⁺ PMAs were increased in peripheral blood of patients with active TB. CD14⁺CD41⁺ PMAs highly expressed triggering receptors expressed on myeloid cells (TREMs)-like transcript-1 (TLT-1), P-selectin (CD62P), and CD40L. Our in vitro study found that platelets from patients with active TB aggregate with monocytes to induce IL-1β and IL-6 production by monocytes. Importantly, we identified that TLT-1 was required for formation of PMAs. The potential TLT-1 ligand was expressed and increased on CD14⁺ monocytes of patients with TB determined by using TLT-1 fusion protein (TLT-1 Fc). Blocking of ligand-TLT-1 interaction with TLT-1 Fc reduced PMA formation and IL-1β and IL-6 production by monocytes. Further results demonstrated that PMAs induced IL-10 production by B cells (B10) dependent on IL-1β, IL-6, and CD40L signals in a coculture system. Moreover, TLT-1 Fc treatment suppressed B10 polarization via blocking PMA formation. Taking all of these data together, we elucidated that TLT-1 promoted PMA-mediated B10 polarization through enhancing IL-1β, IL-6, and CD40L origin from PMAs, which may provide potential targeting strategies for TB disease treatment.

IL8 and IL16 levels indicate serum and plasma quality

BACKGROUND

Longer pre-centrifugation times alter the quality of serum and plasma samples. Markers for such delays in sample processing and hence for the sample quality, have been identified.

METHODS

Twenty cytokines in serum, EDTA plasma and citrate plasma samples were screened for changes in concentration induced by extended blood pre-centrifugation delays at room temperature. The two cytokines that showed the largest changes were further validated for their "diagnostic performance" in identifying serum or plasma samples with extended pre-centrifugation times.

RESULTS

In this study, using R&D Systems ELISA kits, EDTA plasma samples and serum samples with a pre-centrifugation delay longer than 24 h had an IL16 concentration higher than 313 pg/mL, and an IL8 concentration higher than 125 pg/mL, respectively. EDTA plasma samples with a pre-centrifugation delay longer than 48 h had an IL16 concentration higher than 897 pg/mL, citrate plasma samples had an IL8 concentration higher than 21.5 pg/mL and serum samples had an IL8 concentration higher than 528 pg/mL.

CONCLUSIONS

These robust and accurate tools, based on simple and commercially available ELISA assays can greatly facilitate qualification of serum and plasma legacy collections with undocumented pre-analytics.

HLA class I antibodies trigger increased adherence of monocytes to endothelial cells by eliciting an increase in endothelial P-selectin and, depending on subclass, by engaging FcγRs

Ab-mediated rejection (AMR) of solid organ transplants is characterized by intragraft macrophages. It is incompletely understood how donor-specific Ab binding to graft endothelium promotes monocyte adhesion, and what, if any, contribution is made by the Fc region of the Ab. We investigated the mechanisms underlying monocyte recruitment by HLA class I (HLA I) Ab-activated endothelium. We used a panel of murine mAbs of different subclasses to crosslink HLA I on human aortic, venous, and microvascular endothelial cells and measured the binding of human monocytic cell lines and peripheral blood monocytes. Both anti-HLA I murine (m)IgG1 and mIgG2a induced endothelial P-selectin, which was required for monocyte adhesion to endothelium irrespective of subclass. mIgG2a but not mIgG1 could bind human FcγRs. Accordingly, HLA I mIgG2a but not mIgG1 treatment of endothelial cells significantly augmented recruitment, predominantly through FcγRI, and, to a lesser extent, FcγRIIa. Moreover, HLA I mIgG2a promoted firm adhesion of monocytes to ICAM-1 through Mac-1, which may explain the prominence of monocytes during AMR. We confirmed these observations using human HLA allele-specific mAbs and IgG purified from transplant patient sera. HLA I Abs universally elicit endothelial exocytosis leading to monocyte adherence, implying that P-selectin is a putative therapeutic target to prevent macrophage infiltration during AMR. Importantly, the subclass of donor-specific Ab may influence its pathogenesis. These results imply that human IgG1 and human IgG3 should have a greater capacity to trigger monocyte infiltration into the graft than IgG2 or IgG4 due to enhancement by FcγR interactions.