A rapid technique for measuring leukocyte chemotaxis in vivo

Eotaxin selectively binds heparin. An interaction that protects eotaxin from proteolysis and potentiates chemotactic activity in vivo

An important feature of chemokines is their ability to bind to the glycosaminoglycan (GAG) side chains of proteoglycans, predominately heparin and heparan sulfate. To date, all chemokines tested bind to immobilized heparin in vitro, as well as cell surface heparan sulfate in vitro and in vivo. These interactions play an important role in modulating the action of chemokines by facilitating the formation of stable chemokine gradients within the vascular endothelium and directing leukocyte migration, by protecting chemokines from proteolysis, by inducing chemokine oligomerization, and by facilitating transcytosis. Despite the importance of eotaxin in eosinophil differentiation and recruitment being well established, little is known about the interaction between eotaxin and GAGs and the functional consequences of such an interaction. Here we report that eotaxin binds selectively to immobilized heparin with high affinity (K(d) = 1.23 x 10(-8) M), but not to heparan sulfate or a range of other GAGs. The interaction of eotaxin with heparin does not promote eotaxin oligomerization but protects eotaxin from proteolysis directly by plasmin and indirectly by cathepsin G and elastase. In vivo, co-administration of eotaxin and heparin is able to significantly enhance eotaxin-mediated eosinophil recruitment in a mouse air-pouch model. Furthermore, when heparin is co-administered with eotaxin at a concentration that does not normally result in eosinophil infiltration, eosinophil recruitment occurs. In contrast, heparin does not enhance eotaxin-mediated eosinophil chemotaxis in vitro, suggesting protease protection or haptotactic gradient formation as the mechanism by which heparin enhances eotaxin action in vivo. These results suggest a role for mast cell-derived heparin in the recruitment of eosinophils, reinforcing Th2 polarization of inflammatory responses.

Deficient eosinophil chemotaxis-promoting activity of genetically normal mast cells transplanted into subcutaneous tissue of Mitfmi-vga9/Mitfmi-vga9 mice: comparison of the activity and mast cell distribution pattern with KitW/KitW-vMice

Despite the practical lack of mast cells in the skin tissue of WBB6F(1)-Kit(W)/Kit(W-v), the skin tissue of WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice contains one third of mast cells than that of WBB6F(1)-+/+ mice. We attempted to investigate the function of the decreased but appreciable number of mast cells in the skin of WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice. The substance P (SP)-induced eosinophil infiltration was examined using air-bleb assay. The air-bleb membrane was composed of the subcutaneous connective tissue. Unexpectedly, we found that the air-bleb membranes formed in the back of WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice contained no mast cells. The WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice showed impaired SP-induced eosinophil infiltration as observed in WBB6F(1)-Kit(W)/Kit(W-v) mice, indicating that mast cells detected in the dermis of WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice did not help SP-induced eosinophil infiltration. Subcutaneous transplantation of cultured mast cells from WBB6F(1)-+/+ mice normalized SP-induced eosinophil infiltration in WBB6F(1)-Kit(W)/Kit(W-v) mice but not in WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice. The greater number and the more dispersed distribution pattern of mast cells that appeared in the subcutaneous connective tissue of WBB6F(1)-Kit(W)/Kit(W-v) mice after the transplantation appeared to explain the difference between WBB6F(1)-Kit(W)/Kit(W-v) and WBB6F(1)-Mitf(mi-vga9)/Mitf(mi-vga9) mice.

Repeated antigen exposure is necessary for the differentiation, but not the initial proliferation, of naive CD4(+) T cells

The mechanisms that regulate CD4(+) T cells responses in vivo are still poorly understood. We show here that initial Ag stimulation induces in CD4(+) T cells a program of proliferation that can develop, for at least seven cycles of division, in the absence of subsequent Ag or cytokine requirement. Thereafter, proliferation stops but can be reinitiated by novel Ag stimulation. This initial Ag stimulation does not however suffice to induce the differentiation of naive CD4(+) T cells into effector Th1 cells which requires multiple contacts with Ag-loaded APC. Thus, recurrent exposure to both Ag and polarizing cytokines appears to be essential for the differentiation of IFN-gamma-producing cells. Ag and cytokine availability therefore greatly limits the differentiation, but not the initial proliferation, of CD4(+) T cells into IFN-gamma-producing cells.

Relationship between interleukin-5 and eotaxin in regulating blood and tissue eosinophilia in mice

The mechanism of cooperation between IL-5 and eotaxin for the selective accumulation of eosinophils at sites of allergic inflammation is unknown. In this investigation we have used IL-5 deficient mice to define the relationship between this cytokine and eotaxin in the regulation of blood eosinophilia and eosinophil homing and tissue accumulation. Both IL-5 and eotaxin could independently induce a rapid and pronounced blood eosinophilia in wild type mice when administered systemically. In contrast, only eotaxin induced a pronounced blood eosinophilia in IL-5 deficient mice. The eosinophilic response induced by intravenous eotaxin in wild type mice did not correlate with a significant reduction in the level of bone marrow eosinophils, whereas intravenous IL-5 resulted in depletion of this store. These results suggest the existence of two mechanisms by which eosinophils can be rapidly mobilized in response to intravenous eosinophil chemoattractants; first, mobilization of an IL-5 dependent bone marrow pool, and second, an eotaxin-induced sequestration of eosinophils from tissues into the blood. Subcutaneous injection of eotaxin induced a local tissue eosinophilia in wild type mice but not in IL-5 deficient mice. Furthermore, tissue eosinophilia in wild type mice, but not in IL-5 deficient mice, was enhanced by adoptive transfer of eosinophils or the administration of intravenous IL-5. However, pretreatment of IL-5 deficient mice with intraperitoneal IL-5 for 72 h restored eosinophil homing and tissue accumulation in response to subcutaneous eotaxin. We propose that eotaxin secreted from inflamed tissue may play an important role in initiating both blood and tissue eosinophilia in the early phases of allergic inflammation. Furthermore, IL-5 is not only essential for mobilizing eosinophils from the bone marrow during allergic inflammation, but also plays a critical role in regulating eosinophil homing and migration into tissues in response to eotaxin and possibly other specific chemotactic stimuli.

Effects of non-specific immunopotentiators in experimental Schistosoma mansoni infection. II. Corynebacterium parvum

The effects of Corynebacterium parvum on host protection, tissue reaction and "in vivo" chemotaxis in Schistosoma mansoni infected mice were studied. The C. parvum was given intraperitoneally using a dose of 0.7 mg, twice a week (for 4 weeks), thirty days before (prophylactic treatment) or after infection (curative treatment). The host protection was evaluated through the recovery of adult worms by liver perfusion and was lower in the prophylactic group as compared to the control group (p = 0.018), resulting in 44% protection. The "in vivo" leukocyte response in both prophylactic and curative groups was higher as compared to the infected/non treated group (p = 0.009 and p = 0.003, respectively). Tissue reactions were described in the experimental and control groups, but there were not remarkable differences among them. The possible biological implications and relevance of the findings for the defensive response of the host and control of schistosomiasis are discussed.

Inhibitory effect of KBT-3022, a new anti-platelet agent, on infiltration of polymorphonuclear leukocytes induced by leukotriene B4 or formyl-methionyl-leucyl-phenylalanine in mice

We devised a method for evaluating polymorphonuclear leukocyte (PMN) infiltration in vivo employing an air bleb technique combined with measurement of myeloperoxidase (MPO) activity, and the effects of some anti-platelet agents were evaluated. KBT-3022 (ethyl 2-[4,5-bis(4-methoxyphenyl)thiazol-2-yl]pyrrol-1-ylacetate) and cilostazol inhibited the increase in MPO activity in the connective tissue around the air bleb induced by leukotriene B4 (LTB4) and formyl-methionyl-leucyl-phenylalanine (fMLP). Indomethacin inhibited only the fMLP-induced increase in MPO activity, but ticlopidine hydrochloride and acetylsalicylic acid had no effect. Histologic observation confirmed the inhibition of PMN infiltration by KBT-3022. These results indicate that KBT-3022 may be a potent inhibitor of both LTB4- and fMLP-induced infiltration of PMNs.

"In vivo" leukocyte chemotaxis in experimental mice Schistosoma mansoni infection

The "in vivo" chemotaxis was studied in C57Bl/10 mice 10, 30, 50 and 60 days after a Schistosoma mansoni infection in comparison to a control group (uninfected mice). Staphylococcal protein A was injected into a connective tissue air pouch of control and experimental mice and the leukocyte chemotaxis was counted. A decrease in polymorphonuclear (PMN) leukocyte response was found in infected mice in comparison to the control group (p < 0.05). The 10 day infected mice showed a decreased PMN leukocyte response respecting the control group (p < 0.05) and this finding became more evident 30 and 50 days post-infection. Although the PMN leukocyte response of 60 day infected mice increased in comparison to 50 day infected animals, it was still significantly lower the control response. The mononuclear leukocyte response was not significantly different between infected or uninfected mice.

Association between expression of immunoglobulin G-binding proteins by group A streptococci and virulence in a mouse skin infection model

In this study, we developed a mouse model of skin infection to test the association between expression of immunoglobulin-binding proteins by and infectivity of group A streptococci. Group A streptococci capable of crossing tissue barriers and establishing a lethal systemic infection in mice showed a higher level of immunoglobulin-binding protein expression. The group A streptococci recovered from the spleen of a mouse that died following a skin infection were found to be more virulent when injected into the skin of naive mice. Together, these results suggest that immunoglobulin-binding protein expression by group A streptococci correlates with their ability to establish invasive skin infections.

Substance P-induced granulocyte infiltration in mouse skin: the mast cell-dependent granulocyte infiltration by the N-terminal peptide is enhanced by the activation of vascular endothelial cells by the C-terminal peptide

Previous studies have shown that substance P induces granulocyte infiltration in mouse skin, which is mediated through mast cell degranulation. However, it is not yet known whether the direct effect of substance P on vascular endothelial cells is involved in the granulocyte infiltration in the skin. To solve this issue, we used the N-terminal peptide substance P1-9 (SP1-9), which is active for mast cells but inactive for vascular endothelial cells, and the C-terminal peptide SP6-11, which is active for vascular endothelial cells but inactive for mast cells, since substance P activates both mast cells and vascular endothelial cells. The subcutaneous administration of substance P (10(-7)-10(-5)M) caused granulocyte (neutrophil and eosinophil) infiltration in the skin of BALB/c mice 6 h after the injection. SP1-9 (10(-5)-10(-4) M) also caused granulocyte infiltration of mouse skin which was associated with mast cell degranulation. In contrast, SP6-11 (10(-7)-10(-4) M), which was found to increase the vascular permeability of endothelial cells in mouse skin, induced no significant granulocyte infiltration nor mast cell degranulation. However, SP6-11 (10(-5)-10(-4) M) enhanced SP1-9-induced granulocyte infiltration in the skin without any significant increase in mast cell degranulation. We conclude that substance P causes granulocyte infiltration in mouse skin through both mast cell degranulation induced by the N-terminal peptide of substance P and the activation of vascular endothelial cells induced by the C-terminal peptide of substance P.

Complement activation and antibody binding by pneumolysin via a region of the toxin homologous to a human acute-phase protein

Pneumolysin, a membrane-damaging toxin, is known to activate the classical complement pathway. We have shown that 1 microgram ml-1 of pneumolysin can activate complement, which is a much lower level than observed previously. We have identified two distinct regions of pneumolysin which show homology with a contiguous sequence within acute-phase proteins, including human C-reactive protein (CRP). Site-directed mutagenesis of the pneumolysin gene was used to change residues common to pneumolysin and CRP. Some of the modified toxins had a reduced ability both to activate complement and bind antibody. We suggest that the ability of pneumolysin to activate complement is related to its ability to bind the Fc portion of immunoglobulin G.

[Effects of non-specific immunopotentiators on experimental Schistosoma mansoni infection. I. Levamisole]

The effects of levamisole on the histopathological changes, host's resistance and "in vivo" chemotaxis in Schistosoma mansoni experimental infection of C57Bl/10 inbred mice were studied. Prophylactic treatment resulted in an increase in the number of adult worms obtained by perfusion and also increased the mortality rate (p < 0.05). The histopathological changes (liver and intestines) were similar in all the groups. A significant reduction of "in vivo" chemotaxis occurred in infected control mice as well as in those submitted to prophylactic treatment with levamisole. Chemotactic activity reached the same levels of normal control mice (non-infected and non-treated with levamisole), when the curative scheme was used. Levamisole seems to increase the susceptibility of inbred C57Bl/10 mice to the infection with S. mansoni when administered prior to the infection and increase the chemotactic activity to normal levels when given after infection.

Human granulocytes and granulocytes from other species demonstrate differences in chemotactic responsiveness to oxidized N-formyl-methionyl-leucyl-phenylalanine

1. Oxidation of the methionine of N-formyl-methionyl-leucyl-phenylalanine to the sulfoxide or sulfone derivative results in the loss of the peptide's chemotactic activity for human granulocytes. 2. The oxidized peptides are chemotactic for human monocytes; however, 10- to 100-fold higher concentrations are required for optimal monocyte chemotaxis. 3. Mouse, guinea pig and rabbit granulocytes, and the WBC264-9 human-mouse hybrid cell line migrated to the oxidized peptides and required 10- to 1000-fold higher concentrations of the oxidized peptides to elicit optimal chemotactic responses. 4. Human granulocytes appear to be unique in their lack of responsiveness to oxidized derivatives.

Staphylococcal protein A (SpA): a potent in vivo chemotactic agent for rat leucocytes

Staphylococcal protein A had strong chemotactic attraction in vivo to rat leucocytes. Doses as small as 5 micrograms attracted net leucocytes into experimental pellets in 6 h. 50 micrograms Staphylococcal protein A showed maximum chemotactic activity and does greater or less than 50 micrograms attracted less net leucocytes into experimental pellets. The effect of time on the chemoattraction of 50 micrograms Staphylococcal protein A showed that it was an early chemoattractant. Chemotactic activity for this dose, shown by the chemotactic index, reached a peak at 6 h followed by maximum leucocytic infiltration, and almost disappeared completely at 12 h. Leucocytic migration into control pellets rose from 3 h and reached a peak at 12 h (later than the chemotactic peak). Staphylococcal protein A also showed in this study a "later reaction" from 24 to 36 h, resulting in local inflammation of the test site and rise in cellular response.

Growth factors and determinants of wound repair

The application of contemporary biochemical, analytical, and production technology have, in part, clarified the physiologic processes and identified many new factors active in wound repair. A restructuring of the sequence of the reparative events for the wound environment followed the identification of an array of hormonal polypeptides and growth factors. Deterrents of the early phases of repair include neoplasms and therapeutic doses of steroidal and cytotoxic agents. The physiological effects of these agents are rapidly reversed following their removal with a resultant enhancement of wound tear strength and wound energy. The use of synthetic growth hormone and recombinant DNA-produced polypeptide may reverse the deleterious wound healing events initiated in the injured and tumor-bearing host.

Nerve growth factor accelerates the early cellular events associated with wound healing

The effects of injecting nerve growth factor (NGF) into subdermal air sacs on the backs of mice was studied. Sequential infiltration of cells into the lining of the sacs was observed. The initial cell type to infiltrate was the polymorphonuclear leukocyte, followed by highly vacuolated mononuclear cells, and then by fibroblast-like cells. This resembles the classical pattern of cellular responses during the normal process of wound healing. The kinetics for the peak accumulation of each cell type were dependent upon the concentration of NGF injected, and significant acceleration of infiltration of each cell type was observed with as little as 1 nM NGF. A similar acceleration of cellular infiltration was observed when mice were injected with the synthetic chemotactic peptide n-formyl-methionyl-leucyl-phenylalanine. This finding suggests that application of any chemotactic factor to wound sites may lead to accelerated tissue repair and an enhanced rate of wound contraction. The observation that NGF can act as a chemotactic factor in vivo may explain its ability to accelerate the healing of experimentally induced wounds in mice.