Human leukocyte migration inhibitory factor (LIF). I. Effect of synthetic and naturally occurring esterase and protease inhibitors

Human leucocyte response to migration inhibitory activity from lymphocytes. Modification by aprotinin, Tranexamic acid and phenylmethyl sulfonylfluoride

Human lymphokines can elicit several effects associated with inflammation, e.g. leucocyte migration inhibition and fibrinolysis. These effects can be assessed in vitro by the leucocyte migration agarose technique (LMAT) and the leucocyte migration fibrinolysis technique (LMFT). The present study shows that preincubation of normal leucocytes with aprotinin, tranexamic acid and phenyl-methyl-sulfonylfluoride (PMSF) reduces or abolishes their migration inhibition response to leucocyte migration inhibition factor. The compounds exert this effect at non-toxic concentrations, which do not otherwise interfere with migration or fibrinolysis, and are non-toxic as estimated by PHA stimulation of lymphocytes. The LMFT is more sensitive to the modifying effect than the LMAT. The effect of aprotinin and tranexamic acid is reversible, the effect of PMSF is irreversible.

Rat lymphokines control the migration of nonsensitized lymphocytes

We investigated whether mediators released from rat splenic mononuclear cells could control the in vitro migration of nonsensitized resting rat lymphocytes. Rat splenocytes stimulated with concanavalin A, other mitogens, or histamine release three lymphokines that alter rat lymphocyte migration. A positive chemokinetic factor, termed lymphocyte chemoattractant factor (LCF), has a molecular weight (MW) between 50 and 70 kDa. Two negative chemokinetic lymphokines can also be identified; lymphocyte migration inhibitory factor (LyMIF, MW 25-45 kDa) and a high MW inhibitor (HWMI, MW greater than 70 kDa). Lymphokines were destroyed by heat as well as by treatment with neuraminidase and trypsin. The action of LCF and LyMIF was prevented by phenylmethylsulfonylfluoride, a specific serine esterase inhibitor, and the action of LyMIF was also blocked by alpha-L-fucose. The discovery of these mediators provides the opportunity to study the importance of such chemokinetic lymphokines in animal models of disease.

Inhibition of human neutrophil migration by supernatants from Hodgkin's disease-derived cell lines

The contribution of defective neutrophil function to the increased susceptibility to infection observed in patients with Hodgkin's disease is unclear. We describe cell-directed inhibition of normal human neutrophil migration by serum-free culture supernatants of the Hodgkin-derived cell line L428 KSA, tentatively termed Hodgkin-derived leucocyte factor (HDLF). This factor inhibits both random migration and migration toward different chemoattractants, appears to bind to the cell surface and is stable at 56 degrees C but destroyed at 100 degrees C. Hodgkin-derived leucocyte factor also stimulates basal neutrophil superoxide production but the cells remain fully responsive to n-formyl-methionylleucylphenylalanine. Gel filtration chromatography shows a single peak of migration-inhibitory and superoxide-stimulatory activity at approximately 70,000 g mol-1. Hodgkin-derived leucocyte factor migration inhibition persists in neutrophils from a patient with chronic granulomatous disease. Activity of HDLF is completely destroyed by trypsin but unaffected by the protease inhibitor phenyl-methylsulphonylfluoride. Hodgkin's factor appears to be different from previously described neutrophil migration inhibitory factors.

Potentiation of neutrophil aggregation by human leukocyte inhibitory factor

The current studies were designed to extend our investigations on the ability of the lymphokine leukocyte inhibitory factor (LIF) to function as a neutrophil activator. Specifically, we investigated whether LIF could modulate neutrophil (PMN) aggregation. Aggregation was measured as the increase in light transmission using a Payton aggregometer. We found that up to 16 units of LIF was not able to directly induce PMN clumping. However, when preincubated with 0.5-16 units LIF for 10 min, PMN aggregation was significantly enhanced in a dose-dependent manner after stimulation with 10(-7) M FMLP (94.5 +/- 3.1%), 20 nM leukotriene B4 (183.1 +/- 8.2%), and 100 micrograms guinea pig serum-opsonized zymosan (29.8 +/- 8.6%). While the LIF preparation used in these studies was highly purified, specificity for the LIF effect was demonstrated by the ability of several treatments to prevent augmentation of aggregation including: (1) the competitive binding of LIF to one of its substrates: benzoyl-arginine-ethyl-ester; (2) the blocking of PMN LIF receptors with N-acetyl-D-glucosamine; and (3) phenylmethylsulfonylfluoride treatment of the LIF preparation. As aggregation is thought to represent the in vitro correlate to adherence, these studies provide further evidence for a proinflammatory role for LIF in vivo.

Enhancement of the function of neutrophil type-1 and type-3 complement receptors by human leukocyte inhibitory factor (LIF)

The lymphokine leukocyte inhibitory factor (LIF) has previously been documented to enhance several neutrophil (PMN) functions, including stimulated chemotaxis and superoxide generation, phagocytosis and adherence of opsonized targets, and antibody-dependent cellular cytotoxicity. The present studies were designed to investigate the effects of LIF on PMN function mediated by the complement components C3b and C3bi. LIF induced a dose-dependent increase in superoxide production generated by opsonized zymosan (up to 97.1 +/- 31.4% at 16 U LIF/ml; P less than 0.01). While neither control nor LIF-treated PMN were capable of inducing phagocytosis of either C3b- or C3bi-opsonized sheep erythrocytes (E) directly, exposure to LIF caused a significant (P less than 0.05) increase in their adherence to E (137.4 and 59.4%, respectively). Specificity for complement receptor function was confirmed by the ability of anti-CR1 antibody to block adherence of LIF-treated PMN to EAC3b (77.0% inhibition) and anti-CR3 antibody to block adherence to EAC3bi (70.2% inhibition). Increased C3b and C3bi function may have been due, at least in part, to increased expression of their respective surface membrane receptors. Thus, using indirect immunofluorescence, LIF induced a 38.2% increase in fluorescence of the anti-CR1 antibody and a 96.1% increase in anti-CR3 binding. These studies describe an additional mechanism through which LIF may have an important pro-inflammatory role in vivo.

Demonstration of leukocyte inhibitory factor in human Schistosomiasis mansoni and its evaluation from patients in an endemic setting

Leukocyte migration inhibitory Factor (LIF) is produced by the peripheral blood mononuclear cells (PBMN) of most patients with Schistosoma mansoni infection upon their exposure to soluble egg antigens (SEA). PBMN of some patients also respond to adult worm (SWAP) antigens by LIF production. LIF is stable at 37 degrees C for 60 min but is sensitive to heating at 56 degrees C for even 30 min. The serine protease inhibitor PMSF destroyed LIF activity at concentrations of 10(-2) to 10(-3) M. Concanavalin A stimulated production of detectable levels of LIF by 8 hr, while SEA and SWAP did so by 15 and 39 hr, respectively. PBMN of healthy normal controls did not produce LIF upon exposure to SEA or SWAP. PBMN of a few field controls (stool negative subjects from an endemic area) produced detectable LIF activity when exposed to SEA or SWAP. PBMN from most infected (stool positive) patients from an endemic area produced LIF when exposed to SEA and only occasionally did so to SWAP. Previous studies have shown that most often only the PBMN of former, cured patients, and not chronically infected patients, produce the lymphokine activity termed mitogenic factor (MF). The current data indicate that because LIF is primarily produced by actively infected patients, its production may be controlled by different immunoregulatory mechanisms. Furthermore, although most SEA-related responses are highly immunoregulated in active, chronically infected patients, SEA appears to be a better stimulus for patient PBMN production of LIF than SWAP.

Increased polymorphonuclear leukocyte cGMP levels induced by the human lympholine, leukocyte migration inhibitory factor (LIF)

The possible involvement in vitro of 3', t'-cyclic GMP (cGMP) in the mechanism of action of the lymphokine, leukocyte migration inhibitory factor (LIF), was investigated. Partially purified LIF-rich supernatants, but not their control counterparts, induced a 2-fold increase in the cGMP levels of purified human polymorphonuclear (NMN) leukocytes. The effect was no influenced by heat-inactivated horse serum; it was manifested within 3 min of exposure to LIF and it subsided within 180 min. LIF and the supernatant factor responsible for the cGMP-generating effect were both rendered inactive by treatment with the serine esterase and protease inhibitor, phenylmethylsulfonyl fluoride, indicating that these factors are closely related, if not identical. A potent phosphodiesterase inhibitor, dipyridamole (2 x 10(-4) M), induced a 3- to 5-fold increase in PMN leukocyte cGMP levels, but combined treatment with purified LIF and dipyridamole did not add to this effect. This suggests that the cGMP-generating factor acts on the biochemical pathway that degrades cGMP.

Substrate specificity of the human lymphokine leucocyte migration-inhibitory factor (LIF): radioenzymic assay and inhibition by cGMP

The human lymphokine, leucocyte migration-inhibitory factor (LIF), appears to be a serine esterase and protease by virtue of its susceptibility to the irreversible enzyme inhibitor, phenylmethylsulfonyl fluoride (PMSF), and by the ability of arginine esters and amides to protect LIF against PMSF-induced inactivation. In this paper, three methods are described by which putative substrates for LIF may be investigated. Thus, molecules satisfying the substrate specificities of this lymphokine should (1) protect LIF against inactivation by PMSF, (2) reduce LIF activity in vitro on polymorphonuclear leucocytes, and (3) reduce the esterolytic activity of purified LIF-rich supernatants. The first two reactions were tested by means of the leucocyte migration agarose technique; the third reaction was tested by a sensitive enzyme assay using tritiated tosyl arginine methyl ester as substrate. Guanosine 3',5'-cyclic monophosphoric acid, which is capable of protecting LIF against PMSF-induced inhibition, also inhibited the esterolytic activity of the purified LIF preparation. Four synthetic oligopeptide substrates for trypsin, thombin and plasmin were investigated. Only one, the thrombin- and trypsin-specific benzoyl-phenylalanyl-valyl-agarine-p-nitroanilide, possessed high affinity for the LIF molecule and may therefore prove to be a potent substrate for this lymphokine.

Leukocyte migration inhibitory factor: a serine esterase released by stimulated human lymphocytes. Kinetic analysis and inhibition by cyclic GMP

Lymphocytes, stimulated with concanavalin A, release small amounts of non-immunoglobulin, highly reactive proteins called lymphokines. One of these, a serine esterase, termed leukocyte migration inhibitory factor according to its function in vitro, is found in supernatants of stimulated human lymphocytes at concentrations less than 1 ng/ml. The esterase was purified in good yield and its esterolytic activity was measured by a sensitive radioenzymic assay. The kinetics of the esterolytic activity were studied and the effect of various nucleotides examined. Competitive inhibition of esterolysis was seen with cyclic GMP at concentrations down to 10(-7) M, and with 2',3'-cyclic CMP at a concentration of 10(-3) M. A role of this esterase, not only as a mediator acting upon polymorphonuclear leukocytes, but also as an intracellular regulator of lymphocyte activation, is discussed.

Human leucocyte migration inhibitory factor (LIF). V. Specific regulation of the lymphokine serine protease activity by 3',5'-cGMP and, possibly, 2',3'-cCMP

The cyclic nucleotides guanosine 3',5'-cyclic monophosphoric acid (3',5'-cGMP) and cytidine 2',3'-cyclic monophosphoric acid (2',3'-cCMP) but not cyclic phosphodiesters derived from the bases adenine and uracil preserved LIF activity against the blocking effect of the serine protease inhibitor phenylmethylsulphonyl fluoride (PMSF). Phosphomonoesters derived from guanosine and cytidine as well as 2',3'-cGMP and 3',5'-cCMP were all inactive, indicating specificity for phosphodiester bonds and their respective positions in the two active nucleotides. The protection afforded by 3',5'-cGMP and 2',3'-cCMP was dose dependent. Thus, using 10(-3) M PMSF, 3',5'-cGMP was active at concentrations higher than 10(-5) to 10(-4) M, and 2',3'-cCMP at concentrations higher than 3 X 10(-4) to 10(-3) M. The more pronounced LIF-inhibitory effect obtained by increased concentrations of PMSF could be overcome by raising the levels of the nucleotides, indicating that the interactions between PMSF and the nucleotides with LIF were mutally exclusive. The possibility that 3',5'-cGMP and perhaps 2',3'-cCMP function as modulators of LIF is discussed, and models for the function of this lymphokine are proposed.

The indirect assay for leukocyte migration inhibitory factor (LIF)--standardization and the effect of pH

In the indirect assay for leukocyte migration inhibitory factor (LIF), lymphokine-rich supernatants were obtained by culture of stimulated lymphocytes and then tested for LIF activity in agarose plates using purified granulocytes as target cells. Studies on the standardization of the conditions under which LIF acts on the target cells are described, with emphasis on the use of "standard" supernatants of known LIF activity and the influence of pH on the action of LIF and the sensitivity of the assay. The observation that LIF activity is reduced when the ambient pH falls below 7.2 is suggested as an explanation firstly for the "escape" phenomenon seen particularly in capillary tube assays for LIF, and secondly for the reduced sensitivity of the capillarly tube assay in comparison with the corresponding agarose plate assay.

Effect of human leucocyte migration inhibitory factor (LIF) on 3', 5'-cyclic AMP levels of peripheral blood leucocytes

The possible involvement of 3', 5'-cyclic AMP (cyclic AMP) in the mechanism of action of leucocyte migration inhbitory factory (LIF) was tested. LIF-treated human peripheral blood leucocytes were incubated at 37 degrees C for various times between 0 and 22 h. The concentrations of cyclic AMP in these cultures did not differ from those in controls. Furthermore, LIF did not affect the cellular release of cyclic AMP. Neither when testing purified neutrophils, which are the prime targets of LIF action, an effect of LIF was found. Cyclic AMP levels decreased with time of incubation, whether testing mononuclear cells (92 per cent lymphocytes), purified neutrophils (98 per cent), or buffy coat cells (72 per cent neutrophils; 22 per cent lymphocytes). However, a transient and as yet unexplained increase in the cyclic AMP levels of the latter mixed population of cells was manifested within 10 to 30 min of incubation.

Human leukocyte migration inhibitory factor (LIF). II. Partial biochemical characterization of the substrate specificities for this lymphokine

Previously reported experiments suggested that an esterase or a protease, or both, might participate in the expression of human leukocyte migration inhibitory factor (LIF). To clarify this further, a wide variety of simple ester were tested for the ability to protect LIF against inactivation by the serine esterase inhibitor phenylmethylsulfonyl fluoride (PMSF). alpha-N-benzoyl-L-arginine ethylester (BAEE), a typical trypsin substrate, and bis-p-nitrophenyl phosphate (BNPP), a phosphodiester, were the only esters capable of retaining LIF activity in the presence of PMSF. Agents chemically closely related to these esters were inactive. Moreover, the protection afforded by BAEE and BNPP was the king that would be anticipated if the esters and irreversible inhibitor competed for the same site on LIF. Baee and BNPP also protected against inactivation by di-isopropylfluorophosphate (DFP), another irreversible serine esterase inhibitor. In addition, LIF-treated leukocytes partly escaped migration inhibition in the presence of BAEE and BNPP, respectively. These results indicate that human LIF contains a serine residue necessary for lymphokine activity. It is still not proved, however, that LIF as an enzyme is capable of hydrolyzing BAEE and BNPP, although it seems highly possible. The substrate specificities of a putative LIF enzyme are discussed on the basis of the chemical structure of BAEE and BNPP.