Cytological study on the regulation of lymphocyte homing in the chicken spleen during LPS stimulation

The immune function of the chicken spleen depends on its different compartments of red and white pulps, but little is known about the mechanism underlying lymphocyte homing towards the different compartments. In the present study, the role of lymphocyte homing in the chicken spleen was investigated during lipopolysaccharide (LPS) stimulation. Morphological analysis demonstrated the cuboidal endothelial cells of the splenic sheathed capillary facilitated the passage of lymphocyte homing to the chicken spleen. The tissue-specific adhesion molecules- vascular cell adhesion molecule-1 (VCAM-1) and mucosal addressin cell adhesion molecule-1 (MADCAM-1) expressed on the sheathed capillary, which suggested the high endothelial venule (HEV)-like vessels of the chicken spleen. Electron microscope analysis showed LPS activated the endothelium of the sheathed capillary and recruited lymphocytes to the chicken spleen. Transferring of 5, 6- carboxyfluorescein diacetate, succinimidyl ester (CFSE) labeled lymphocytes depicted the rout of lymphocyte homing to the compartments of the chicken spleen was from the white pulp to the red pulp. Furthermore, the mRNA and protein levels of adhesion molecular integrin β1 and VCAM-1 increased after LPS stimulation. The mechanism underlying the integrin β1 and VCAM-1 during LPS stimulation might be associated with the integrin linked kinase (ILK)- dependent regulation of protein kinase B (PKB/AKT). This study firstly shows lymphocyte homing in the chicken spleen after LPS-induced inflammation. These results contribute to our knowledge of comparative immunology and provide a better means for investigating the pharmacological strategies concerning the possible role of lymphocyte homing in inflammation and immunological reactions in infectious disease.

Definitive activation of endogenous antitumor immunity by repetitive cycles of cyclophosphamide with interspersed Toll-like receptor agonists

Many cancers both evoke and subvert endogenous anti-tumor immunity. However, immunosuppression can be therapeutically reversed in subsets of cancer patients by treatments such as checkpoint inhibitors or Toll-like receptor agonists (TLRa). Moreover, chemotherapy can leukodeplete immunosuppressive host elements, including myeloid-derived suppressor cells (MDSCs) and regulatory T-cells (Tregs). We hypothesized that chemotherapy-induced leukodepletion could be immunopotentiated by co-administering TLRa to emulate a life-threatening infection. Combining CpG (ODN 1826) or CpG+poly(I:C) with cyclophosphamide (CY) resulted in uniquely well-tolerated therapeutic synergy, permanently eradicating advanced mouse tumors including 4T1 (breast), Panc02 (pancreas) and CT26 (colorectal). Definitive treatment required endogenous CD8+ and CD4+ IFNγ-producing T-cells. Tumor-specific IFNγ-producing T-cells persisted during CY-induced leukopenia, whereas Tregs were progressively eliminated, especially intratumorally. Spleen-associated MDSCs were cyclically depleted by CY+TLRa treatment, with residual monocytic MDSCs requiring only continued exposure to CpG or CpG+IFNγ to effectively attack malignant cells while sparing non-transformed cells. Such tumor destruction occurred despite upregulated tumor expression of Programmed Death Ligand-1, but could be blocked by clodronate-loaded liposomes to deplete phagocytic cells or by nitric oxide synthase inhibitors. CY+TLRa also induced tumoricidal myeloid cells in naive mice, indicating that CY+TLRa's immunomodulatory impacts occurred in the complete absence of tumor-bearing, and that tumor-induced MDSCs were not an essential source of tumoricidal myeloid precursors. Repetitive CY+TLRa can therefore modulate endogenous immunity to eradicate advanced tumors without vaccinations or adoptive T-cell therapy. Human blood monocytes could be rendered similarly tumoricidal during in vitro activation with TLRa+IFNγ, underscoring the potential therapeutic relevance of these mouse tumor studies to cancer patients.