An L-selectin ligand distinct from P-selectin glycoprotein ligand-1 is expressed on endothelial cells and promotes neutrophil rolling in inflammation

Neutrophils recruited from the blood are key players in the innate immune response. Selectins play critical roles in neutrophil recruitment by mediating their tethering and rolling in inflamed venules. While the roles of P- and E-selectin in this process are well established, the mechanisms of L-selectin-mediated neutrophil recruitment remain elusive. One proposal is that tethering is mediated by L-selectin on flowing neutrophils interacting with P-selectin glycoprotein ligand-1 (PSGL-1) on adherent neutrophils. To clarify whether L-selectin-mediated neutrophil recruitment depends entirely on PSGL-1, we examined the impact of L-selectin deficiency in mice with a PSGL-1-deficient background. L-selectin and PSGL-1 double-knockout mice exhibited a higher increase in their peripheral blood neutrophil count and a worse defect in neutrophil recruitment into the inflamed peritoneum than PSGL-1-deficient mice. Intravital microscopy of inflamed cremaster muscle venules showed that L-selectindeficiency or antibody blockade of L-selectin reduced the residual leukocyte rolling in PSGL-1-deficient mice. Flow cytometric analyses showed that the endothelial cells from the cremaster muscle bound L-selectin in a PSGL-1-independent manner. These results provide evidence for the existence of an L-selectin ligand distinct from PSGL-1 in inflammation and indicate that such a ligand is expressed on endothelial cells, promoting neutrophil rolling in vivo.     

CD19 and CD22 expression reciprocally regulates tyrosine phosphorylation of Vav protein during B lymphocyte signaling

B cell development and humoral immune responses are controlled by signaling thresholds established through the B lymphocyte antigen receptor (BCR) complex. BCR signaling thresholds are differentially regulated by the CD22 and CD19 cell surface receptors in vivo. B cells from CD22-deficient mice exhibit characteristics of chronic stimulation and are hyper-responsive to BCR crosslinking with augmented intracellular Ca²⁺ responses. By contrast, B cells from CD19-deficient mice are hypo-responsive to transmembrane signals. To identify signaling molecules involved in the positive and negative regulation of signaling thresholds, the signal transduction pathways activated after BCR crosslinking were examined in CD22- and CD19-deficient B cells. These comparisons revealed that tyrosine phosphorylation of Vav protein was uniquely augmented after BCR or CD19 crosslinking in CD22-deficient B cells, yet was modest and transient after BCR crosslinking in CD19-deficient B cells. Ligation of CD19 and CD22 in vivo is likely to positively and negatively regulate BCR signaling, respectively, because CD19 crosslinking was more efficient than BCR crosslinking at inducing Vav phosphorylation. However, simultaneous crosslinking of CD19 with the BCR resulted in a substantial decrease in Vav phosphorylation when CD22 was expressed. Thus, the differential regulation of Vav tyrosine phosphorylation by CD19 and CD22 may provide a molecular mechanism for adjusting BCR signaling thresholds.     

Tumor-targeted T cells modified to secrete IL-12 eradicate systemic tumors without need for prior conditioning

Adoptive cell therapy with tumor-targeted T cells is a promising approach to cancer therapy. Enhanced clinical outcome using this approach requires conditioning regimens with total body irradiation, lymphodepleting chemotherapy, and/or additional cytokine support. However, the need for prior conditioning precludes optimal application of this approach to a significant number of cancer patients intolerant to these regimens. Herein, we present preclinical studies demonstrating that treatment with CD19-specific, chimeric antigen receptor (CAR)-modified T cells that are further modified to constitutively secrete IL-12 are able to safely eradicate established disease in the absence of prior conditioning. We demonstrate in a novel syngeneic tumor model that tumor elimination requires both CD4(+) and CD8(+) T-cell subsets, autocrine IL-12 stimulation, and subsequent IFNγ secretion by the CAR(+) T cells. Importantly, IL-12-secreting, tumor-targeted T cells acquire intrinsic resistance to T regulatory cell-mediated inhibition. Based on these preclinical data, we anticipate that adoptive therapy using CAR-targeted T cells modified to secrete IL-12 will obviate or reduce the need for potentially hazardous conditioning regimens to achieve optimal antitumor responses in cancer patients.     

CD19 expression in B cells is important for suppression of contact hypersensitivity

Contact hypersensitivity (CHS) is a cutaneous immune reaction mediated mainly by antigen-specific effector T cells and is regarded as a model for Th1/Tc1-mediated inflammation. However, recent reports have suggested pivotal roles of B cells in CHS. CD19 serves as a positive B-cell response regulator that defines signaling thresholds critical for B-cell responses. In the current study, we assessed the role of the B-cell-specific surface molecule CD19 on the development of CHS by examining CD19-deficient mice. Although CD19-deficient mice are hyposensitive to a variety of transmembrane signals, CD19 loss resulted in increased and prolonged reaction of CHS, suggesting an inhibitory role of CD19 expression in CHS. Sensitized lymph nodes and elicited ear lesions from CD19-deficient mice exhibited Th1/Tc1-shifted cytokine profile with increased interferon-gamma expression and decreased interleukin-10 expression. Adoptive transfer experiments revealed that CD19 expression in recipient mice was required for optimal suppression of CHS response, indicating its role in the elicitation phase. Furthermore, spleen B cells, especially marginal zone B cells, from wild-type mice were able to normalize exaggerated CHS reactions in CD19-deficient mice. Thus, CD19 expression in B cells is critical for termination of CHS responses, possibly through the function of regulatory B cells.     

Interleukin-4 and interleukin-5 map to human chromosome 5 in a region encoding growth factors and receptors and are deleted in myeloid leukemias with a del(5q)

Interleukin-4 (IL-4) is a potent mediator of growth and differentiation of cells of several hematopoietic lineages. Interleukin-5 (IL-5) is a lineage-specific hematopoietic growth factor that stimulates the production of eosinophils and eosinophil colonies from normal human bone marrow cells. By using somatic cell hybrids and in situ chromosomal hybridization, we localized the IL-4 and IL-5 genes to human chromosome 5 at bands q23-31, a chromosomal region that is frequently deleted [del(5q)] in patients with myeloid disorders. By in situ hybridization, the IL-4 and IL-5 genes were found to be deleted in the 5q- chromosome of four patients with refractory anemia (RA) or therapy-related acute nonlymphocytic leukemia (t-ANLL), who had a del(5q). Thus a small segment of chromosome 5 contains IL-4, IL-5, IL- 3, and GM-CSF as well as other genes such as CD14 and EGR1. Our findings that each of these genes was deleted in the 5q- chromosome suggest that loss of function of one or more of these genes may play an important role in the pathogenesis of hematologic disorders associated with a del(5q).     

Asynchronous globin chain synthesis in rabbit reticulocyte lystates induced by hemin-controlled repressor

To define further the role of hemin-controlled repressor (HCR) in globin synthesis, we studied its effect on the synthesis of individual globin chains in a rabbit reticulocyte lysate cell-free system. In the presence of HCR there was a marked globin chain imbalance, resulting in a lowered alpha/beta ratio. These findings in vitro may have relevance to certain clinical heme deficiency states in which a similar globin chain imbalance has been observed.     

Fluorescence in situ hybridization mapping of translocations and deletions involving the short arm of human chromosome 12 in malignant hematologic diseases

Translocations and deletions of the short arm of chromosome 12 [t(12p) and del(12p)] are common recurring abnormalities in a broad spectrum of hematologic malignant diseases. We studied 20 patients and one cell line whose cells contained 12p13 translocations and/or 12p deletions using fluorescence in situ hybridization (FISH) with phage, plasmid, and cosmid probes that we previously mapped and ordered on 12p12-13. FISH analysis showed that the 12p13 translocation breakpoints were clustered between two cosmids, D12S133 and D12S142, in 11 of 12 patients and in one cell line. FISH analysis of 11 patients with deletions demonstrated that the deletions were interstitial rather than terminal and that the distal part of 12p12, including the GDI-D4 gene and D12S54 marker, was deleted in all 11 patients. Moreover, FISH analysis showed that cells from 3 of these patients contained both a del(12p) and a 12p13 translocation and that the affected regions of these rearrangements appeared to overlap. We identified three yeast artificial chromosome (YAC) clones that span all the 12p13 translocation breakpoints mapped between D12S133 and D12S142. They have inserts of human DNA between 1.39 and 1.67 Mb. Because the region between D12S133 and D12S142 also represents the telomeric border of the smallest commonly deleted region of 12p, we also studied patients with a del(12p) using these YACs. The smallest YAC, 964c10, was deleted in 8 of 9 patients studied. In the other patient, the YAC labeled the del(12p) chromosome more weakly than the normal chromosome 12, suggesting that a part of the YAC was deleted. Thus, most 12p13 translocation breakpoints were clustered within the sequences contained in the 1.39 Mb YAC and this YAC appears to include the telomeric border of the smallest commonly deleted region. Whether the same gene is involved in both the translocations and deletions is presently unknown.     

HTLV-III antibody and T-cell subset ratios in haemophiliacs and their spouses

44% of 63 British patients with either haemophilia A or B were HTLV-III antibody positive (HTLV-VIII+). HTLV-III+ was more frequent in high factor VIII concentrate users and 75% of severely affected haemophilia A patients were HTLV-III+. All eight patients who were exposed to factor IX concentrate were HTLV-III-. 17 haemophilia A patients who received only British made factor VIII concentrate (average 12,000 units/year) were HTLV-III-. Two of 63 patients had evidence of a pre-AIDS type symptom complex and both were HTLV-III+. Information from a cohort of 21 Liverpool haemophiliacs suggests that HTLV-III was first introduced into this country in 1981. OKT4/T8 ratios were abnormal in 52% of 21 patients studied but this finding was not confined to either HTLV-III+ or HTLV-III- individuals. The spouses of 14 HTLV-III+ haemophiliacs were all HTLV-III-.