A population of lymphoid cells from several animal species, including man, was identified through a membrane receptor which binds sheep red blood cells treated with antibody and complement. When cells from different lymphoid organs were incubated with EAC at 37°C, only part of the lymphocytes (named CRL) bound EAC and formed rosettes, and this interaction was shown to be C3-dependent. Mouse lymphoid cells could be specifically depleted of CRL by allowing them first to interact with EAC and then submitting the mixture to ultracentrifugation in a gradient of BSA. After ultracentrifugation, a population of cells containing 95% or more of non-CRL were recovered from the upper layers of the gradient. In addition to their different abilities to bind EAC, CRL and non-CRL from mouse lymphoid organs could be distinguished by the following properties: (a) CRL adhered preferentially to nylon wool at 37°C in the presence of mouse serum. (b) After differential flotation in a gradient of BSA, a significantly higher proportion of CRL were recovered from the upper layers of the gradient. (c) The population of CRL contained most of the lymphocytes bearing immunoglobulin determinants on their membranes. (d) The distribution of CRL was quite different among lymphocytes obtained from various lymphoid organs, and they were never found in the thymus. (e) The membrane receptor for EAC was not detected in plaque-forming cells of mice which had been previously immunized with burro red cells. CRL and non-CRL could not be distinguished by their life span, as they were found in similar proportions among long-lived and short-lived lymphocytes from mouse peripheral lymph nodes. The function of this receptor on the membrane of certain lymphoid cells may be related to (a) the trapping and localization of antigen in lymphoid organs or (b) the localization of lymphoid cells in inflammatory sites.

Macrophages possess on their plasma membranes receptors for the Fc portion of IgG and for the third complnent of complement (1,2) . These receptors are important in the performance of some of the functions of these cells . The Fc receptors mediate both attachment and ingestion of IgG-coated particles (3,4) . However, the complement receptors of mouse peritoneal macrophages and of human and rabbit alveolar macrophages mediate binding of C3-coated particles to the macrophage surface but do not appear to mediate ingestion of these particles (3,5,6) .In several experimental systems, immunization or chronic intracellular infection has been shown to alter certain functions of the immunized or infected animal's macrophages (7-13) . Intraperitoneal injection of some foreign substances such as thioglycollate medium and bacillus Calmette-Guérin (BCG)' effects functional changes in the animal's peritoneal macrophages similar to those changes induced by immunization or intracellular infection . Macrophages from such animals are termed activated macrophages . They spread more readily on glass ; contain more mitochondria, lysosomes, and lysosomal enzymes ; demonstrate increased spontaneous and postphagocytic glucose carbon-1 oxidation ; and possess greater phagocytic, microbicidal, and microbistatic activity than their nonactivated counterparts (7-13) . A qualitative difference in enzyme function between activated and nonactivated macrophages was recently demonstrated by Unkeless et al. (14) . They found that macrophages from mice injected intraperitoneally with thioglycollate medium produce and secrete a neutral protease, plasminogen activator, while macrophages from control mice do not .In this paper, we present the results of our studies of the functions of the Fc receptors and complement receptors of activated and nonactivated mouse peritoneal macrophages . We find that the quantity of ingestion mediated by the Yc

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This investigation focused on the role played by cold-insoluble globulin (CIg, plasma fibronectin) in monocyte function. Surface-bound CIg mediated a concentration-dependent of human blood monocytes to gelatin-coated surfaces. CIg also mediated the binding of gelatin-coated particles such as latex beads or tanned erythrocytes to surface-bound human monocytes. However, CIg did not mediate particle ingestion. Subfractionated CIg that was highly enriched in monomeric forms (zone II CIg, mol wt 190,000-235,000) was less effective than were fractions enriched in dimeric forms (zone I CIg, mol wt 450,000) in promoting monocyte attachment. Binding of CIg to a gelatin or plastic surface occurred in the absence of divalent cations, but monocyte attachment to CIg-coated surfaces required divalent cations, Mg++ being much more effective than Ca++. Cation-dependent cell attachment was reversible in that bound cells could be released by treatment with EDTA. Serum-mediated binding of monocytes to gelatin-coated plastic dishes was a result of its content of CIg because the binding activity was abolished by removal of CIg from serum, and could be restored by readdition of purified CIg. Treatment of monocytes with trypsin abolished subsequent cell attachment to CIg-gelatin surfaces or particles. Expression of certain other known monocyte membrane receptors (Fc and C3b) was markedly enhanced as a result of CIg-monocyte interaction. These several observations indicate that monocytes bear membrane receptors (termed receptor cold-insoluble globulin) for surface-bound CIg.

National blood donor screening for West Nile virus (WNV) RNA using minipool nucleic acid amplification testing (MP-NAT) was implemented in the United States in July 2003. We compiled national NAT yield data and performed WNV immunoglobulin M (IgM) testing in 1 WNV-epidemic region (North Dakota). State-specific MP-NAT yield, antibody seroprevalence, and the average time RNA is detectable by MP-NAT were used to estimate incident infections in 2003. WNV donor screening yielded 944 confirmed viremic donors. MP-NAT yield peaked in August with >0.5% of donations positive for WNV RNA in 4 states. Peak IgM seroprevalence for North Dakota was 5.2% in late September. The average time viremia is detectable by MP-NAT was 6.9 days (95% confidence interval [CI] 3.0-10.7). An estimated 735,000 (95% CI 322,000-1,147,000) infections occurred in 2003, with 256 (95% CI 112-401) infections per neuroinvasive case. In addition to preventing transfusion-transmitted WNV infection, donor screening can serve as a tool to monitor seasonal incidence in the general population.

Although the risk of infection by blood transfusion is relatively low, breakthrough infections still occur, Transfusion-related fatalities caused by infections continue to be reported, and blood is not tested for many potentially dangerous pathogens. The current paradigm for increasing the safety of the blood supply is the development and implementation of laboratory screening methods and restrictive donor criteria. When considering the large number of known pathogens and the fact that pathogens continue to emerge, it is clear that the utility of new tests and donor restrictions will continue to be a challenge when considering the cost of developing and implementing new screening assays, the loss of potential donors, and the risk of testing errors. Despite improving the safety of blood components, testing remains a reactive approach to blood safety. The contaminating organisms must be identified before sensitive tests can be developed. In contrast, pathogen inactivation is a proactive strategy designed to inactivate a pathogen before it enters the blood supply. Almost all pathogen inactivation technologies target nucleic acids, allowing for the inactivation of a variety of nucleic acid-containing pathogens within plasma, platelets, or red blood cells thus providing the potential to reduce transfusion-transmitted diseases. However, widespread use of a pathogen inactivation technology can only be realized when proven safe and efficacious and not cost-prohibitive.

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The complement receptor of the macrophage membrane recognizes particle-bound C3b but does not recognize particle-bound C3d. C3-b-coated sheep erythrocytes were bound to macrophages via their C3b receptors, and the preparations were then incubated with either latex particles or opsonized pneumococci (test particles). Macrophages ingested the test particles, but erythrocytes were not ingested; they remained bound to C3b receptors of the macrophage plasma membrane. Thus, a signal initiating ingestion via one type of receptor is not transmitted to all receptors which have the potential to mediate phagocytosis.