Identification of a subpopulation of lymphocytes in human peripheral blood cytotoxic to autologous fibroblasts.
A naturally occurring subpopulation of human peripheral blood lymphocytes is cytotoxic to autologous and/or allogeneic fibroblasts. The autocytotoxic lymphocytes have a receptor for the third component of complement and for aggregated gamma globulin, do not form rosettes with sheep red blood cells, and are not removed by passage through nylon. The autocytotoxic subpopulation is not present in the thymus and tonsils of normal children or in the peripheral blood of individuals with X-linked agammaglobulinemia. Fibroblast absorption experiments demonstrate that the autocytotoxic cells are "sensitized" to antigens expressed on allogeneic fibroblasts in addition to the antigens expressed on autologous cells. Some normal individuals have a second subpopulation of lymphocytes that may "regulate" the autocytotoxic cells. The relevance of these observations to the murine autocytotoxic cells is discussed. (+info)
Contributory and exacerbating roles of gaseous ammonia and organic dust in the etiology of atrophic rhinitis.
Pigs reared commercially indoors are exposed to air heavily contaminated with particulate and gaseous pollutants. Epidemiological surveys have shown an association between the levels of these pollutants and the severity of lesions associated with the upper respiratory tract disease of swine atrophic rhinitis. This study investigated the role of aerial pollutants in the etiology of atrophic rhinitis induced by Pasteurella multocida. Forty, 1-week-old Large White piglets were weaned and divided into eight groups designated A to H. The groups were housed in Rochester exposure chambers and continuously exposed to the following pollutants: ovalbumin (groups A and B), ammonia (groups C and D), ovalbumin plus ammonia (groups E and F), and unpolluted air (groups G and H). The concentrations of pollutants used were 20 mg m-3 total mass and 5 mg m-3 respirable mass for ovalbumin dust and 50 ppm for ammonia. One week after exposure commenced, the pigs in groups A, C, E, and G were infected with P. multocida type D by intranasal inoculation. After 4 weeks of exposure to pollutants, the pigs were killed and the extent of turbinate atrophy was assessed with a morphometric index (MI). Control pigs kept in clean air and not inoculated with P. multocida (group H) had normal turbinate morphology with a mean MI of 41.12% (standard deviation [SD], +/- 1. 59%). In contrast, exposure to pollutants in the absence of P. multocida (groups B, D, and F) induced mild turbinate atrophy with mean MIs of 49.65% (SD, +/-1.96%), 51.04% (SD, +/-2.06%), and 49.88% (SD, +/-3.51%), respectively. A similar level of atrophy was also evoked by inoculation with P. multocida in the absence of pollutants (group G), giving a mean MI of 50.77% (SD, +/-2.07%). However, when P. multocida inoculation was combined with pollutant exposure (groups A, C, and E) moderate to severe turbinate atrophy occurred with mean MIs of 64.93% (SD, +/-4.64%), 59.18% (SD, +/-2.79%), and 73.30% (SD, +/-3.19%), respectively. The severity of atrophy was greatest in pigs exposed simultaneously to dust and ammonia. At the end of the exposure period, higher numbers of P. multocida bacteria were isolated from the tonsils than from the nasal membrane, per gram of tissue. The severity of turbinate atrophy in inoculated pigs was proportional to the number of P. multocida bacteria isolated from tonsils (r2 = 0.909, P < 0.05) and nasal membrane (r2 = 0.628, P < 0.05). These findings indicate that aerial pollutants contribute to the severity of lesions associated with atrophic rhinitis by facilitating colonization of the pig's upper respiratory tract by P. multocida and also by directly evoking mild atrophy. (+info)
Human herpesvirus 8 seroprevalence and evaluation of nonsexual transmission routes by detection of DNA in clinical specimens from human immunodeficiency virus-seronegative patients from central and southern Italy, with and without Kaposi's sarcoma.
In order to investigate the seroprevalence of human herpesvirus 8 (HHV-8) infection in central and southern Italy, sera from human immunodeficiency virus (HIV)-seronegative subjects, with and without Kaposi's sarcoma (KS), were analyzed by immunofluorescence assay, using BC-3, a cell line latently infected with HHV-8. High titers of antibody against HHV-8 lytic and latent antigens were detected in all 50 KS patients studied, while in 50 HIV-seronegative subjects without KS, 32 (64%) were found positive for HHV-8 antibodies. Titers in the sera of these patients were lower than those for KS patients. This data suggests that HHV-8 infection is not restricted to KS patients and that the prevalence of HHV-8 infection in the general population may be correlated with differing rates of prevalence of KS in different parts of the world. In view of these findings, possible nonsexual transmission routes were evaluated. Nested PCR was used to test for the presence of HHV-8 DNA in saliva, urine, and tonsillar swabs from KS and non-KS patients. In KS patients, 14 out of 32 tonsillar swabs (43.7%), 11 out of 24 saliva samples (45.8%), and just 2 out of 24 urine samples (8.3%) tested positive for HHV-8 DNA. In the control group, on the contrary, none of the 20 saliva and 20 urine specimens was positive for HHV-8 DNA; only 1 out of 22 tonsillar swabs gave a positive result. This data supports the hypothesis that HHV-8 infects the general population in a latent form. The reactivation of viral infection may result in salivary shedding of HHV-8, contributing to viral spread by nonsexual transmission routes. (+info)
Nonimmunoglobulin gene hypermutation in germinal center B cells.
Somatic hypermutation is the most critical mechanism underlying the diversification of Ig genes. Although mutation occurs specifically in B cells during the germinal center reaction, it remains a matter of debate whether the mutation machinery also targets non-Ig genes. We have studied mutations in the 5' noncoding region of the Bcl6 gene in different subtypes of lymphomas. We found frequent hypermutation in follicular lymphoma (25 of 59 = 42%) (germinal center cell origin) and mucosa-associated lymphoid tissue (MALT) lymphoma (19 of 45 = 42%) (postgerminal center), but only occasionally in mantle cell lymphoma (1 of 21 = 4.8%) (pregerminal center). Most mutations were outside the motifs potentially important for transcription, suggesting they were not important in lymphomagenesis but may, like Ig mutation, represent an inherent feature of the lymphoma precursor cells. Therefore, we investigated their normal cell counterparts microdissected from a reactive tonsil. Bcl6 mutation was found in 13 of 24 (54%) clones from the germinal centre but only in 1 of 24 (4%) clones from the naive B cells of the mantle zone. The frequency, distribution, and nature of these mutations were similar to those resulting from the Ig hypermutation process. The results show unequivocal evidence of non-Ig gene hypermutation in germinal center B cells and provide fresh insights into the process of hypermutation and lymphomagenesis. (+info)
Toward a role of dendritic cells in the germinal center reaction: triggering of B cell proliferation and isotype switching.
We have reported previously that in vitro generated dendritic cells (DC) can directly regulate B cell responses. Recently, germinal center DC (GCDC) were identified within B cell follicles. Due to their particular localization, we have tested in the present study whether GCDC could contribute to key events characteristic of the GC reaction. Our present results demonstrate that 1) ex vivo GCDC induce a dramatic GC B cell expansion upon CD40 and IL-2 activation and drive plasma cell differentiation, 2) this property is shared by GCDC and blood DC, but not by Langerhans cells, 3) IL-12 production by GCDC is critical in GC B cell expansion and differentiation, and 4) importantly, GCDC also induce IL-10-independent isotype switching toward IgG1. These observations support the novel concept that GCDC directly contribute to the germinal center reaction. (+info)
Mucosal dendritic cells and immunodeficiency viruses.
Dendritic cells [DCs] have been implicated in the pathogenesis of human immunodeficiency virus type 1 (HIV-1). When skin was used as a model for mucosae, the cutaneous DC-T cell milieu allowed the growth of HIV-1 and much of the newly produced virus could be detected in multinucleated DC-T cell syncytia. Such virus replication occurs irrespective of the genetic subtype, the syncytium- and non-syncytium-inducing capacities of the viruses, and whether they are classified as T cell- or macrophage-tropic. Similar DC-syncytia have been identified within the mucosal surfaces of the tonsillar tissue of HIV-1-infected persons. More recently, it was demonstrated that DC-T cell mixtures from the skin, mucosae, and blood of healthy macaques similarly support the replication of simian immunodeficiency virus. In both the human and monkey systems, active virus replication requires the presence of both DCs and T cells. Further studies using the macaque model are underway to elucidate the role of DCs in the transmission and spread of HIV infection. (+info)
Antigen receptor engagement selectively induces macrophage inflammatory protein-1 alpha (MIP-1 alpha) and MIP-1 beta chemokine production in human B cells.
We show herein that B cell Ag receptor (BCR) triggering, but not stimulation by CD40 mAb and/or IL-4, rapidly induced the coordinated expression of two closely related T cell chemoattractants, macrophage inflammatory protein-1 beta (MIP-1 beta) and MIP-1 alpha, by human B cells. Naive, memory, and germinal center B cells all produced MIP-1 alpha/beta in response to BCR triggering. In contrast to MIP-1 alpha/beta, IL-8, which is spontaneously produced by germinal center B cells but not by naive and memory B cells, was not regulated by BCR triggering. Culturing follicular dendritic cell-like HK cells with activated B cells did not regulate MIP-1 alpha/beta production, but it did induce production of IL-8 by HK cells. Microchemotaxis assays showed that CD4+CD45RO+ T cells of the effector/helper phenotype actively migrated along a chemotactic gradient formed by BCR-stimulated B cells. This effect was partially blocked by anti-MIP-1 beta and anti-CC chemokine receptor 5 Ab, but not by anti-MIP-1 alpha Ab suggesting that MIP-1 beta plays a major role in this chemoattraction. Since maturation of the B cell response to a peptide Ag is mostly dependent on the availability of T cell help, the ability of Ag-stimulated B cells to recruit T cells via MIP-1 alpha/beta, may represent one possible mechanism enabling cognate interactions between rare in vivo Ag-specific T and B cells. (+info)
Age-dependent altered proportions in subpopulations of tonsillar lymphocytes.
Age-related changes in functional subsets of lymphocytes may influence the potential to build up immune responses. In particular, the capacity of tonsillar lymphocytes to counter infections may be altered during ageing. In order to address this question we investigated the proportional distribution of several subsets of tonsillar T and B cells with regard to ageing. Tonsils were derived from 119 patients between 2 and 65 years of age. Lymphocyte subsets were monitored by three-colour fluorescence of relevant CD markers in flow cytometry. As a general tendency the percentage of CD3+ T cells steadily increased whereas that of CD19+ B cells decreased at the same time. No significant differences were observed between lymphocytes of patients with and without inflammatory history of the tonsils. The percentage of CD8+ T cells declined whereas that of CD4+ T cells increased during the same time span. CD45RA+ T cells increased during the first two decades of life and gradually decreased thereafter. In contrast, CD45RO+ T cells showed an opposite trend. No differences were seen in the population of CD3-/CD56+ natural killer (NK) cells. The mature B cell marker CD40 showed no significant changes during ageing. However, CD38+ B cells, representing B cells of late maturation stages, dramatically declined up to the age of 65. In a similar manner the CD5+ subpopulation of B cells decreased during ageing. Substantial changes in major tonsillar T and B cell populations as shown in this study may have an impact on the ageing process of the immune system. (+info)