Macrophage migration inhibitory factor in thymus

Purification of thymic macrophage migration inhibitory factor (MIF)

Aqueous extracts of the thymus of animals which had been challenged immunologically have been shown to contain MIF activity. This MIF could be purified by precipitation with 70% ethanol, concentrated by ultrafiltration between 30,000 and 50,000 daltons, isoelectrically focused at pH 6.8-7.1, and electrophoresed on preparative acrylamide gels. The resulting product is electrophoretically homogeneous at pH 4.3 in polyacrylamide-gel electrophoresis and SDS-gel electrophoresis. It has a molecular weight of 36,000 daltons. It is trypsin- and neuraminidase-labile and is thermostable. It degrades and reassembles in electrophoresis at pH 7.0. It is not chemotactic for macrophages but apparently activates them phagocytically. It has no proteolytic activity.

Properties of lymphocyte chemotactic factor (lymphotactin) in thymus

Aqueous extracts of calf thymus from immunologically stimulated animals contain trypsin- and neuraminidase-labile macromolecules with molecular weights of less than 30,000 daltons which will specifically attract chemotactically lymphocytes. This activity we ascribe to "lymphotactin."

The biochemistry of lymphocyte-derived mediators of immunological inflammation

Evidence is presented to indicate that there exists in lymphoid tissue, as a result of transforming lymphocytes, a new lymphokine which is chemotactically specific for lymphocytes, called 'lymphotactin'. Lymphotactin has been purified to electrophoretic homogeneity; has a molecular weight of 10,500 D and an isoelectric point of 5.9. Its role in amplifying the immune defense system by recruitment of naive lymphocytes into propinquity with the challenging antigens is suggested. Purification of macrophage migration inhibitory factor from thymus extracts to electrophoretic homogeneity leads to a compound of molecular weight of 36,500 D and an IEP of 6.9. Chemically it contains sialic acid and o-methyl glucopyranoside as its only carbohydrates. Purified MIF activates the macrophage phagocytically. Skin reactive factor and lymph node permeability factor have been isolated and purified and are found to be inhibited by pepstatin and antihistamine and to have an isoelectric point of pH 4.2 and a molecular weight of 50,000--100,000 D. It is believed that this anionic permeability increasing agent actually arises from the lysosomes of macrophages and lymphoblasts (the normal small lymphocyte having essentially no lysosomal organelles). The mononuclear cell infiltration characteristic of crude SRF and LNPF may proceed from their being contaminated with lymphotactin.

Cell-mediated immune phenomena induced by lymphokines from splenic lymphocytes of mice with chronic staphylococcal infection

Splenic lymphocytes from normal mice and from mice displaying delayed hypersensitivity to Staphylococcus aureus were cultured in the presence or absence of specific staphylococcal antigens. The cell-free supernatant fluids from these lymphocyte cultures were assessed for their ability to alter the functional capacities of normal macrophages. It was found that supernatants from staphylococcus-immune cells cultured in vitro with antigen possessed migration inhibitory factor activity and also were capable of stimulating the incorporation of [14C]glucosamine into macrophage membrane glycoproteins. In addition, the lymphokine-containing supernatants were capable of inducing activation of normal macrophages so that they inhibited the multiplication of intracellular Listeria monocytogenes. Although it was not possible to snow any significant enhancement of intracellular killing of S. aureus by the activated macrophages, evidence is presented that suggests that cell-mediated immune responses to S. aureus may significantly enhance pahgocytosis of staphylococci and, thereby, may provide for their rapid clearance from extracellular fluids.