Cell-Cell interaction in erythropoiesis: role of human monocytes

Erythroid burst forming units (BFU-E) are proliferative cells present in peripheral blood and bone marrow which may be precursors of the erythroid colony forming cell found in the bone marrow. To examine the possible role of monocyte-macrophages in the modulation of erythropoiesis, the effect of monocytes on peripheral blood BFU-E proliferation in response to erythropoietin was investigated in the plasma clot culture system. Peripheral blood mononuclear cells from normal human donors were separated into four fractions. Fraction-I cells were obtained from the interface of Ficoll-Hypaque gradients (20-30% monocytes; 60-80% lymphocytes); fraction-II cells were fraction-I cells that were nonadherent to plastic (2-10% monocytes; 90-98% lymphocytes); fraction-III cells were obtained by incubation of fraction-II cells with carbonyl iron followed by Ficoll-Hypaque centrifugation (>99% lymphocytes); and fraction-IV cells represented the adherent population of fraction-II cells released from the plastic by lidocaine (>95% monocytes). When cells from these fractions were cultured in the presence of erythropoietin, the number of BFU-E-derived colonies was inversely proportional to the number of monocytes present (r = ¿0.96, P < 0.001). The suppressive effect of monocytes on BFU-E proliferation was confirmed by admixing autologous purified monocytes (fraction-IV cells) with fraction-III cells. Monocyte concentrations of ¿20% completely suppressed BFU-E activity. Reduction in the number of plated BFU-E by monocyte dilution could not account for these findings: a 15% reduction in the number of fraction-III cells plated resulted in only a 15% reduction in colony formation. These results indicate that monocyte-macrophages may play a significant role in the regulation of erythropoiesis and be involved in the pathogenesis of the hypoproliferative anemias associated with infection and certain neoplasia in which increased monocyte activity and monopoiesis also occur

Cell-Cell Interaction in Erythropoiesis: ROLE OF HUMAN MONOCYTES

Erythroid burst forming units (BFU-E) are proliferative cells present in peripheral blood and bone marrow which may be precursors of the erythroid colony forming cell found in the bone marrow. To examine the possible role of monocyte-macrophages in the modulation of erythropoiesis, the effect of monocytes on peripheral blood BFU-E proliferation in response to erythropoietin was investigated in the plasma clot culture system. Peripheral blood mononuclear cells from normal human donors were separated into four fractions. Fraction-I cells were obtained from the interface of Ficoll-Hypaque gradients (20-30% monocytes; 60-80% lymphocytes); fraction-II cells were fraction-I cells that were nonadherent to plastic (2-10% monocytes; 90-98% lymphocytes); fraction-III cells were obtained by incubation of fraction-II cells with carbonyl iron followed by Ficoll-Hypaque centrifugation (>99% lymphocytes); and fraction-IV cells represented the adherent population of fraction-II cells released from the plastic by lidocaine (>95% monocytes). When cells from these fractions were cultured in the presence of erythropoietin, the number of BFU-E-derived colonies was inversely proportional to the number of monocytes present (r = −0.96, P < 0.001). The suppressive effect of monocytes on BFU-E proliferation was confirmed by admixing autologous purified monocytes (fraction-IV cells) with fraction-III cells. Monocyte concentrations of ≥20% completely suppressed BFU-E activity. Reduction in the number of plated BFU-E by monocyte dilution could not account for these findings: a 15% reduction in the number of fraction-III cells plated resulted in only a 15% reduction in colony formation. These results indicate that monocyte-macrophages may play a significant role in the regulation of erythropoiesis and be involved in the pathogenesis of the hypoproliferative anemias associated with infection and certain neoplasia in which increased monocyte activity and monopoiesis also occur

Classic AIDS in a Sooty Mangabey after an 18-Year Natural Infection

Prevailing theory holds that simian immunodeficiency virus (SIV) infections are nonpathogenic in their natural simian hosts and that lifelong infections persist without disease. Numerous studies have reported that SIV-infected sooty mangabeys (SMs; Cercocebus atys) remain disease free for up to 24 years despite relatively high levels of viral replication. Here, we report that classic AIDS developed after an 18-year incubation in an SM (E041) with a natural SIVsm infection. Unlike that described in previous reports of SIV-related disease in SMs, the SIVsm infecting E041 was not first passaged through macaques; moreover, SM E041 was simian T-cell leukemia virus antibody negative. SM E041 was euthanized in 2002 after being diagnosed with severe disseminated B-cell lymphoma. The plasma virus load had been approximately the same for 16 years when a 100-fold increase in virus load occurred in years 17 and 18. Additional findings associated with AIDS were CD4(+)-cell decline, loss of p27 core antibody, and loss of control of SIVsm replication with disseminated giant cell disease. These findings suggest that the time to development of AIDS exceeds the average lifetime of SMs in the wild and that the principal adaptation of SIV to its natural African hosts does not include complete resistance to disease. Instead, AIDS may develop slowly, even in the presence of high virus loads. However, a long-term relatively high virus load, such as that in SM E041, is consistent with AIDS development in less than 18 years in humans and macaques. Therefore, the results also suggest that SMs have a special mechanism for resisting AIDS development

Noninvasive Detection of New Simian Immunodeficiency Virus Lineages in Captive Sooty Mangabeys: Ability To Amplify Virion RNA from Fecal Samples Correlates with Viral Load in Plasma

The sooty mangabey (SM) (Cercocebus atys) is the natural host of a simian immunodeficiency virus, termed SIVsm, which gave rise to human immunodeficiency virus type 2. Data on the geographic distribution, prevalence, and genetic diversity of SIVsm in the wild remains limited. To address this issue, noninvasive strategies based on screening SM fecal and urine specimens for SIVsm-specific antibodies and virion RNA (vRNA) were developed, and the results were correlated with viral loads in plasma. Twenty-three SIVsm-infected and 27 uninfected SMs were evaluated. Time-matched urine, fecal and plasma samples were collected over a 2-month period from 16 captive naturally infected SMs. The remaining 7 infected and 27 uninfected SMs were sampled once. Each specimen was subjected to enhanced chemiluminescence-Western blot analysis and nested reverse transcriptase (RT) PCR. The results showed that urine was highly sensitive (96%) and specific (100%) for detection of SIVsm antibodies, while fecal detection was much less sensitive (16%). Conversely, vRNA detection was more sensitive in feces (50%) than in urine (2%) samples. Fecal-vRNA detection correlated with viral loads in plasma (P < 0.002). SMs with detectable fecal vRNA had a mean viral load in plasma of 458,006 copies/ml, while those with undetectable fecal vRNA had a mean viral load in plasma of 29,428 copies/ml. Moreover, for every log increase in the viral load in plasma, the odds of detecting virus in fecal samples increased 87-fold. Genetic diversity of SIVsm in the SM colony was characterized by sequencing partial gag (846 bp) and gp43 (439 bp) fragments. Surprisingly, four new SIVsm lineages were identified, two of which were initially detected by fecal RT-PCR. This study documents the suitability of noninvasive methods for the detection and molecular characterization of new SIV variants. These assays will be useful for studying the phylogeny and epidemiology of SIVsm infections in the wild, and they hold promise as tools for investigating natural SIV infections in endangered nonhuman primates

Molecular Epidemiology of Simian T-Cell Lymphotropic Virus Type 1 in Wild and Captive Sooty Mangabeys

A study was conducted to evaluate the prevalence and diversity of simian T-cell lymphotropic virus (STLV) isolates within the long-established Tulane National Primate Research Center (TNPRC) colony of sooty mangabeys (SMs; Cercocebus atys). Serological analysis determined that 22 of 39 animals (56%) were positive for STLV type 1 (STLV-1). A second group of thirteen SM bush meat samples from Sierra Leone in Africa was also included and tested only by PCR. Twenty-two of 39 captive animals (56%) and 3 of 13 bush meat samples (23%) were positive for STLV-1, as shown by testing with PCR. Nucleotide sequencing and phylogenetic analysis of viral strains obtained demonstrated that STLV-1 strains from SMs (STLV-1sm strains) from the TNPRC colony and Sierra Leone formed a single cluster together with the previously reported STLV-1sm strain from the Yerkes National Primate Research Center. These data confirm that Africa is the origin for TNPRC STLV-1sm and suggest that Sierra Leone is the origin for the SM colonies in the United States. The TNPRC STLV-1sm strains further divided into two subclusters, suggesting STLV-1sm infection of two original founder SMs at the time of their importation into the United States. STLV-1sm diversity in the TNPRC colony matches the high diversity of SIVsm in the already reported colony. The lack of correlation between the lineage of the simian immunodeficiency virus from SMs (SIVsm) and the STLV-1sm subcluster distribution of the TNPRC strains suggests that intracolony transmissions of both viruses were independent events

Kuru experiments triggered the emergence of pathogenic SIVmac

No abstract available