Deficiency of prolactin-inducible protein leads to impaired Th1 immune response and susceptibility to Leishmania major in mice.

Although the strategic production of prolactin-inducible protein (PIP) at several ports of pathogen entry into the body suggests it might play a role in host defense, no study has directly implicated it in immunity against any infectious agent. Here, we show for the first time that PIP deficiency is associated with reduced numbers of CD4(+) T cells in peripheral lymphoid tissues and impaired CD4(+) Th1-cell differentiation in vitro. In vivo, CD4(+) T cells from OVA-immunized, PIP-deficient mice showed significantly impaired proliferation and IFN-γ production following in vitro restimulation. Furthermore, PIP-deficient mice were highly susceptible to Leishmani major infection and failed to control lesion progression and parasite proliferation. This susceptibility was associated with impaired NO production and leishmanicidal activity of PIP KO macrophages following IFN-γ and LPS stimulation. Collectively, our findings implicate PIP as an important regulator of CD4(+) Th1-cell-mediated immunity.

Triple Negative Breast Cancer Cells Acquire Lymphocyte Proteins and Genomic DNA During Trogocytosis with T Cells.

Trogocytosis is the process by which a recipient cell siphons small membrane fragments and proteins from a donor cell and may be utilized by cancer cells to avoid immune detection. We observed lymphocyte specific protein expressed by TNBC cells via immunofluorescence imaging of patient samples. Image analysis of CD45RA expression, a T cell specific protein, revealed that all stages of TNBCs express CD45RA. Flow cytometry revealed TNBC cells trogocytose CD45 protein from T cells. We also showed that the acquisition of these lymphoid markers is contact dependent. Confocal and super-resolution imaging further revealed CD45 + spherical structures containing T cell genomic DNA inside TNBC cells after co-culture. Trogocytosis between T cells and TNBC cells altered cancer cell gene expression. Our results revealed that CD45 is obtained by TNBC cells from T cells via trogocytosis and that TNBC cells express CD45 intracellularly and on the membrane. Teaser: TNBC cells acquire small spherical structures from T cells containing lymphocyte-specific membrane proteins and genomic DNA.

Leishmania major-derived lipophosphoglycan influences the host's early immune response by inducing platelet activation and DKK1 production via TLR1/2.

Background: Platelets are rapidly deployed to infection sites and respond to pathogenic molecules via pattern recognition receptors (TLR, NLRP). Dickkopf1 (DKK1) is a quintessential Wnt antagonist produced by a variety of cell types including platelets, endothelial cells, and is known to modulate pro-inflammatory responses in infectious diseases and cancer. Moreover, DKK1 is critical for forming leukocyte-platelet aggregates and induction of type 2 cell-mediated immune responses. Our previous publication showed activated platelets release DKK1 following Leishmania major recognition. Results: Here we probed the role of the key surface virulence glycoconjugate lipophosphoglycan (LPG), on DKK1 production using null mutants deficient in LPG synthesis (Δlpg1- and Δlpg2-). Leishmania-induced DKK1 production was reduced to control levels in the absence of LPG in both mutants and was restored upon re-expression of the cognate LPG1 or LPG2 genes. Furthermore, the formation of leukocyte-platelet aggregates was dependent on LPG. LPG mediated platelet activation and DKK1 production occurs through TLR1/2. Conclusion: Thus, LPG is a key virulence factor that induces DKK1 production from activated platelets, and the circulating DKK1 promotes Th2 cell polarization. This suggests that LPG-activated platelets can drive innate and adaptive immune responses to Leishmania infection.

Prolactin-Inducible Protein: From Breast Cancer Biomarker to Immune Modulator-Novel Insights from Knockout Mice.

The propensity for breast cancers to elicit immune responses in patients is well established. The accumulation of tumor infiltrating lymphocytes within the primary breast tumor has been linked to better prognosis and better response to therapy. The prolactin-inducible protein (PIP) is a 15 kD protein that is expressed under physiological conditions of the breast and is regarded as a marker of mammary differentiation. While highly expressed under pathological conditions of the mammary gland, including breast cancers, PIP is expressed in very few other cancers. Although the function of PIP is not well elucidated, numerous studies suggest that its primary role may be related to host defense and immune modulation. However, evidence to show a direct link between PIP and the immune response has been lacking. In this review, we discuss our recent work with Pip-deficient mice, linking PIP not only to a role in innate immunity but for the first time, providing evidence for a role in cell-mediated immunity. These functional studies in Pip null mice lend new insight into the role of PIP in immunity and suggest that PIP may play a similar immune-regulatory role in breast cancer.