Browsing by Subject "lymphocytes"
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Item Molecular Basis of Cancer Cell Recognition and Killing by Human Natural Killer Cells(2001-05-01) Boles, Kent S.; Bennett, Michale; Leudtke, Robert; Goldfarb, RonaldNatural Killer (NK) cells are a population of lymphocytes vital for the innate immune response. These cells protect the host during the early phase of infection before the adaptive immune response is effective. NK cells are direct effectors via cytoxicity towards neoplastic and infected cells. Additionally, they modulate the immune response by the production of cytokines, most notably interferon y and tumor necrosis factor a. Furthermore, NK cell receptors do not undergo rearrangement. Repetoires of activating and inhibitory receptors regulate the function of NK cells via a balance of signaling. NK cell receptors can broadly be divided by their ligand specificity as well. Most of the known receptors recognize MHC class I molecules and transduce inhibitory signals. This is the basis for the missing self hypothesis espoused by Karre and colleagues. The LY49 molecules server this function in the mouse and are related to the C-type lectins. In primates, a family of killer inhibitory receptors (KIR) appear to play the same role and are in the immunoglobulin (Ig) superfamily of receptors. Whether humans expressed the Ly49 receptors was a fundamental question in NK cell biology. In my attempt to address this issue, I isolated two receptors related to the C-type lectin receptors and localized to the human NK gene complex on chromosome 12 in a region syntenic to where the murine Ly49 genes reside. Functional characterization of these receptors will facilitate our understanding of NK cell biology. Additional activating receptors include the members of the CD2 subset of the immunoglobulin superfamily molecules expressed on NK cells and other leukocytes, including murine 2B4. 2B4 is the high affinity ligand for CD48. Engagement of 2B4 on NK cell surfaces with specific antibodies or CD 48 can trigger cell mediated cytotoxicity, IFN-y secretion, phosphoinositol turnover and NK cell invasiveness. This work describes the isolation and characterization of the human homologue of the 2B4 receptor. The putative peptide has a type I structure with one transmembrane domain. The extracellular region is comprised of two immunoglobulin like domains with six putative N-linked glycosylation sites. The cytoplasmic domain of 2B4 contains unique tyrosine motifs (TxYxxV/I) that associate with src homology 2 domain containing protein (SH2DIA) or signaling lymphocyte activation molecule (SLAM)-associate protein (SAP), whose mutation is the underlying genetic defect in the X-linked lymphoproliferative disease (XLPD). Impaired signaling via 2B4 and SLAM is implicated in the immunopathogenesis of XLPD. CS1 is a novel member of the CD2 subset that contains two of the unique tyrosine motifs present in 2B4 and SLAM. Signaling through 2B4, CS1 and other members of the CD2 subset may play a major role in the regulation of NK cells and other leukocyte functions.Item Molecular Regulation of Interferon Gamma in 2B4-Activated Natural Killer Cells: Functional Role in Tumor Rejection(2001-11-01) Johnson, Lori Ann; Mathew, Porunellor A.; Goldfarb, Ronald H.; Dimitrijevich, S. DanNatural killer cells are a third population of lymphocytes, distinct from T and B cells. NK cells are non-MHC-restricted cytotoxic effector cells which are effective against intracellular pathogens, virally-infected cells and tumor cells. 2B4 is a natural killer cell receptor originally identified in the mouse as a surface molecule involved in non-MHC-restricted killing and enhancement of IFN-γ secretion. The human and rat homologues of 2B4 have recently been cloned in our laboratory. Interferon gamma (IFN-γ) is a cytokine with potent anti-viral and anti-proliferative effects. In addition, this cytokine acts as a global immune regulator by regulating gene expression and serving to attract other immune cells. In this work, we establish the function of human 2B4 in a NK cell line, YT. We have shown that human 2B4 activation induces cytolytic function and enhances IFN-γ release in YT cells. Additionally we show that 2B4’s regulation of IFN-γ occurs at the transcriptional level, both through mRNA stability and increased promoter activity. We also demonstrate that several regions in the IFN-γ promoter respond to 2B4 activation and IFN-γ both separately and together in the rejection of metastatictumor cells in C57B7/6 mice. Our results confirm that both 2B4 and IFN-γ are critical in the rejection of metastatic tumor cells. Through the use of activating monoclonal antibodies, our studies indicate that 2B4’s anti-tumor activity is through IFN-γ as well as through cytolytic function of NK cells.Item T-Helper Cell Responses in Lungs After Immunization and Chronic Respiratory Disease; And Their Association With Pulmonary Inflammation(2001-05-01) Jones, Harlan P.; Simecka, Jerry; Dimitrijevich, S. Dan; Goldfarb, Ronald H.The purpose of these studies was to characterize T helper cell responses in the lungs of mice after immunization and chronic respiratory infection. CD4+ T cells were the major population of T cells resident in the lung in comparison to CD8+ T cells. Polyclonal activation of resident CD4+T cells produced abundant levels of IL-4 in comparison to IFN-γ, indicating that Th2 cells were the major sub-population of CD4+ T cells. In contrast, resident CD8+ T cells were the sole producer of IFN-γ by naïve T lymphocytes. Furthermore, the distribution of T cells was similar between BALB/c, C3H/HeN, C57BL/6 and DBA/2N strains of mice. However differences in the distribution of CD8+T cells, as well as the levels of IL-4 and IFN-y production produced by resident T cells were found between C57 and the other strains of mice tested. These results demonstrate that host genetic factors may be involved in determining host susceptibility to respiratory disease. Differences in the intensity of antigenic stimulation provoke changes in the type of T cell response generated. Intranasal immunization with influenza (FLU) vaccine antigen alone initiated solely an antigen-specific Th2-like response. In contrast, the addition of the potent mucosal adjuvant cholera toxin (CT) in combination with FLU antigen induced not only resident Th2 responses, but also induced antigen-specific Th1-like responses. This change corresponded with a dramatic increase in the number of CD4+ T cells in the lung. Thus, intense immunization of respiratory T cells enhanced resident T helper cell responses, but also promoted the activation of Th1 responses. Chronic respiratory infection also elicited changes in the resident population of T cells consistent with pulmonary inflammatory immune responses. At early stages of infection, CD4+, but not CD8+ T cells increased in number within inductive respiratory lymphoid tissues (lower respiratory nodes [LRNs]). Between day 7 and 14 however, there was a dramatic increase in the number of CD4+ T cells in the lung. Interestingly, CD8+ T cells also increased in the lungs, suggesting their activation along mucosal sites during mycoplasma infection. Mycoplasma-specific IL-4 and IFN-γ production also increased in a tissue-specific/time-dependent manner. IL-4 production was initially observed in the LRNs, whereas significant levels of IL-4 and IFN-γ was produced in both tissues 14 days after infection. In comparison, IFN-γ was the predominate cytokine, produce at 14 days coinciding with pulmonary inflammation. Suggesting that intense activation promoted changes in the resident pulmonary Th2 environment, and possible is a major component of pulmonary inflammatory immune responses. Both CD4+ and CD8= T cells were shown to have a role in modulation of disease severity during mycoplasma disease. Observation of gross pulmonary lesions reveal that mycoplasma infected mice treated with anti-CD8 antibody showed increase clinical signs of disease and pronounced gross pulmonary lesions. Additionally the number of total mononuclear cells increased dramatically in the absence of CD8+ T cells. Thus, CD8+ T cells may have a regulatory role in controlling resident CD4+ T cells that increased 14 days after infection. Chemokine production is known to mediate the recruitment of lymphocytes to enhance the initiation of immunity as well as be responsible for modulating inflammatory responses. We find that mycoplasma increase the number of dendritic cells in the lung 14 days after infection, and stimulated the production of dendritic cell-derived ABCD-1 chemokine. Also, β-chemokine MIP-1α and MIB-1β production was observed during intense immunization as well as during mycoplasma infection. These results provide evidence for a potential mechanism through which changes in resident pulmonary T cell responses occur given the intensity of the immune response generated.Item The Functional Role of Human 2B4 (CD244) Isoforms in Natural Killer Cells(2007-05-01) Rao, Krithi K.; Porunelloor Mathew; Rance Berg; Harlan JonesRao, Krithi K., Functional role of human 2B4 (CD244) isoforms in natural killer cells. Master of Science (Immunology), July, 2007, 66 pp., 15 illustrations, bibliography. Natural killer (NK) cells are a subpopulation of lymphoctyes that play an important role against tumor metastasis and various viral and bacterial infections. NK cell functions are controlled by a balance between positive and negative signals through various receptors. We have identified, cloned, and characterized the 2B4 (CD244) receptor in mice and human. 2B4 is involved in killing cancer cells and virus-infected cells by NK cells. 2B4 is involved in killing cancer cells and virus-infected cells by NK cells. 2B4 is a counter-receptor for CD48 and recent findings show that 2B4-CD48 interactions plan an important role in NK, T and B cell functions. In humans, two isoforms of 2B4, h2B4-A and h2B4-B, are expressed that differ in the extracellular domain. In the present investigation, we have studied the functions of h2B4-A and h2B4-B. Our data demonstrate that these two isoforms differ in their binding affinity for CD48, resulting in differential cytolytic function as well as cytokine production by NK cells. Thus, differential expression of 2B4 isoforms by NK cells may regulate immune responses mediated through 2B4-CD48 interactions.