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Polymorphonuclear leucocyte migration through human dermal fibroblast monolayers is dependent on both beta 2-integrin
1Department of Pediatrics, Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.
Abstract:
Accumulation of leucocytes in inflammation involves their migration through vascular endothelium and then in the connective tissue. We investigated human polymorphonuclear leucocyte (PMNL) migration through a biological barrier of human dermal fibroblasts grown on microporous filters, as a model of PMNL migration in the connective tissue. PMNL did not migrate through a fibroblast monolayer unless a chemotactic factor, e.g. C5a, interleukin-8 (IL-8) or zymosan-activated plasma (ZAP; C5adesArg), was added. This migration was partially inhibited (35-70%, depending on the stimulus) by treatment of PMNL with monoclonal antibody (mAb) to CD18 (beta 2-integrins). Most of the CD18-independent migration was inhibited by mAb to beta 1-integrins (CD29). Inhibition by mAb to beta 1 was observed when the PMNL, but not the fibroblasts, were treated with mAb. The role of beta 1-integrins in PMNL transfibroblast migration was detectable only when the function of the CD11-CD18 complex was blocked, because mAb to beta 1-integrin alone had no significant effect on PMNL migration. Migration induced by C5a was more CD18-independent compared to IL-8 or C5adesArg. The CD18-independent migration was also inhibited by mAb to the beta 1-integrin subunits alpha 5 (of very late antigens-5; VLA-5) and alpha 6 (of VLA-6). Treatment of the fibroblasts (4 hr) with tumour necrosis factor-alpha (TNF-alpha) or IL-1 alpha enhanced C5a-induced PMNL transfibroblast migration and increased the proportion of migration utilizing the CD11-CD18 mechanism. However, TNF-alpha treatment had no effect on the degree of beta 1-integrin-dependent migration. These findings suggest that in response to the chemotactic factors C5a, IL-8 and C5adesArg, PMNL migration in the connective tissue is mediated by both CD11-CD18 (beta 2) and beta 1-integrins on the PMNL. The VLA-5 and VLA-6 members of beta 1-integrins are involved in this process. This is in contrast to PMNL migration across endothelium in this system, which is virtually all CD18 dependent with no significant role for beta 1-integrins.
Insights
Human polymorphonuclear leucocyte (PMNL) migration in connective tissue involves both CD11-CD18 and beta 1-integrins. This study reveals distinct roles for integrins in PMNL transmigration, offering insights into inflammatory responses.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Leukocyte accumulation in inflammation requires migration through endothelium and connective tissue.
- Human polymorphonuclear leucocytes (PMNL) are key inflammatory cells.
Purpose of the Study:
- To investigate PMNL migration through a human dermal fibroblast model of connective tissue.
- To elucidate the roles of CD11-CD18 (beta 2) and beta 1-integrins in this process.
Main Methods:
- Utilized a human dermal fibroblast monolayer on microporous filters as a model for connective tissue.
- Assessed PMNL migration using chemotactic factors (C5a, IL-8, ZAP) and blocking antibodies against CD18 and beta 1-integrins.
- Investigated the effects of TNF-alpha and IL-1 alpha on fibroblast-mediated PMNL migration.
Main Results:
- PMNL migration through fibroblasts required chemotactic factors.
- Migration was partially inhibited by anti-CD18 (beta 2-integrin) antibodies.
- A significant portion of migration was CD18-independent and inhibited by anti-beta 1-integrin antibodies (targeting VLA-5 and VLA-6).
- Beta 1-integrin involvement was evident only when CD18 function was blocked.
- Fibroblast pre-treatment with TNF-alpha or IL-1 alpha enhanced PMNL migration and increased CD18 dependence.
Conclusions:
- PMNL migration in connective tissue is mediated by both CD11-CD18 (beta 2) and beta 1-integrins (VLA-5, VLA-6).
- This contrasts with endothelial transmigration, which is primarily CD18-dependent.
- Inflammatory mediators like TNF-alpha and IL-1 alpha modulate PMNL migration mechanisms.