Human Monocyte Subpopulations Research Articles

Characteristics of human monocyte subpopulations with the use of flow cytometer.

Human monocytes separated from peripheral blood by Ficoll-Hypaque and by adherence to serum-coated dishes showed a bimodal volume distribution measured with a fluorescence activated cell sorter. The rate of the fluorescein diacetate hydrolysis by small monocytes was lower than that of large ones. The majority of large monocytes reacted with sensitized SRBC while only a minority of small monocytes bound sensitized SRBC. Scatchard plots on the binding of FITC-labeled human monoclonal IgG1 to the two subpopulations indicated similar association constants, K = 1.2 +/- 0.3 x 10(5) M-1. The number of FcR was significantly different for the small (3.3 +/- 0.6 x 10(5)) and the large monocytes (10 +/- 1 x 10(5)).

Fc receptors for IgE on a subpopulation of human peripheral blood monocytes.

Fc receptors for IgE on a subpopulation of human peripheral blood monocytes.

Subpopulations of human peripheral granulocyes and monocytes express receptors for IgA.

Receptors for the Fc portion of immunoglobin on human peripheral blood cells were enumerated by rosette formation with ox erythrocytes sensitized with rabbit IgG, IgA, and IgM. A large percentage of purified polymorphonuclear leukocytes and monocytes were found to express receptors for IgA. These receptors were also found to exist on a significantly greater percentage of lymphocytes than was previously observed. The receptors for IgA were specific, as verified by blocking studies using purified human immunogloblins. In addition, some polymorphonuclear leukocytes and monocytes were observed concomitantly to posses independent receptors for both IgG and IgA. These studies may indicate that IgA can cooperate with monocytes or polymorphonuclear leukocytes through receptors for IgA on these cells and perhaps mediate immune defense on mucosal surfaces. Initial studies on antibody-dependent cellular cytotoxicity suggested that IgA alone is ineffectual in supporting cytolysis by nonactivated human peripheral blood cells.

Fc receptors specific for IgE on subpopulations of human lymphocytes and monocytes

Fc receptors for IgE (Fc ϵ) were detected on human lymphocytes and monocytes by rosette assays employing ox (E 0) or chicken (E c) erythrocytes coated with human myeloma IgE. Peripheral blood from normal donors contained 1.2 ± 0.6% Fc ϵ + lymphocytes and 23 ± 8% Fc ϵ + monocytes. Over 90% of the Fc ϵ + lymphocytes were B cells that did not have Fc receptors for IgG (Fcγ). Patients with severe atopic disease and highly elevated IgE levels had significantly higher percentages (7.0 ± 2.0%) of Fc ϵ + lymphocytes. Cells from 18 of 28 established human B lymphoblastoid cell lines were Fc ϵ + ; 16 of these were Fc γ − and only two were Fc ϵ + and Fc γ + . The affinity of monomeric IgE for Fc ϵ receptors on cultured lymphoblastoid cells was relatively low (10 6–10 7 L/M), and the IgE rapidly washed off the cells. Monocytes specifically phagocytosed and lysed IgE-coated 51Cr-labeled E c. These data provide evidence that Fc receptors for IgE are found not only on mast cells and basophilic granulocytes but also on lymphocytes and monocytes. The affinity of monomeric IgE to the Fc receptors of these cell types is much lower than that to mast cells and basophilic granulocytes. The function of Fc ϵ receptors on monocytes is most likely promotion of phagocytosis and lysis of IgE-coated target cells. Fc receptors for IgE on lymphocytes may play a role in the regulation of IgE synthesis.

Lactoferrin acts on Ia-like antigen-positive subpopulations of human monocytes to inhibit production of colony stimulatory activity in vitro.

The relationship between Ia-like antigens (Ia-antigens) on human monocytes and the ability of lactoferrin (LF) to inhibit the production of colony stimulatory activity (CSA) for granulocyte and macrophage colony formation was investigated. Complement-dependent cytotoxicity of human monocytes by antiserum to Ia-antigen-reduced CSA production by 50%. LF decreased CSA production by monocytes but had no influence on monocytes insensitive to anti-Ia and complement. Anti-Ia in the absence of complement had no effect on production of CSA but blocked the inhibitory action of LF. This suggsts that LF inhibits production of CSA from an Ia-antigen-positive subpopulation of human blood monocytes. This may be of relevance to the regulation of myelopoiesis.

Synthesis of prostaglandins by subpopulations of human peripheral blood monocytes

The ability of monocytes/macrophages to regulate various aspects of immunologic responses may in part depend on their release of soluble substances such as prostaglandins. Using quantitative gas-liquid chromatography/mass spectrometry, prostaglandin E 2 was found to be the major prostaglandin synthesized in culture by human peripheral blood monocytes. Subjecting these cells to discontinuous density gradient fractionation demonstrated significant differences in the synthesis of prostaglandins E 2 and E 1 among the resulting monocyte subpopulations.