Chemotaxis of human B lymphocytes to anti-IgD
1Department of Immunology, University of Glasgow.
Insights
Human tonsil B cells show movement in response to anti-immunoglobulin D (IgD). While high concentrations cause general movement (chemokinesis), lower concentrations in gradients induce directed movement (chemotaxis), suggesting antigen receptor-mediated B cell migration.
Area of Science:
- Immunology
- Cell Biology
Background:
- B cells express surface immunoglobulin M (IgM) and IgD, crucial for antigen recognition.
- Interleukin-4 (IL-4) can preactivate B cells, enhancing their responsiveness.
- Antigen receptor engagement is a key signaling pathway in B cell activation and migration.
Purpose of the Study:
- To investigate whether the locomotor response of preactivated B cells to anti-IgD is chemotactic.
- To determine the effect of different concentrations and gradients of anti-IgD on B cell migration.
- To examine the impact of anti-IgD exposure on surface IgD expression.
Main Methods:
- Human tonsil B cells were cultured with IL-4 to induce preactivation.
- A checkerboard filter assay was used to assess B cell migration in response to anti-IgD.
- Various concentrations and concentration gradients of anti-IgD were tested.
- Surface IgD expression was measured after incubation with anti-IgD.
Main Results:
- Preactivated B cells exhibited locomotor responses to anti-IgD at concentrations between 10 ng/ml and 1 microgram/ml.
- High concentrations (100 ng/ml to 1 microgram/ml) of anti-IgD induced chemokinesis but not chemotaxis.
- Lower concentrations (0-50 ng/ml) of anti-IgD in gradients demonstrated chemotaxis.
- Incubation with high-concentration anti-IgD (1 microgram/ml) led to progressive loss of surface IgD, unlike low-concentration exposure (10 ng/ml).
Conclusions:
- B cell migration in response to anti-IgD can be chemotactic at lower concentrations in gradients.
- Higher concentrations of anti-IgD may induce chemokinesis due to receptor downregulation.
- These findings highlight the complex regulation of B cell migration by antigen receptor signaling and antibody concentration.
Abstract:
The resting population of small surface IgM+ and surface IgD+ B cells from the human tonsil can be preactivated by overnight culture in interleukin-4 (IL-4) to show locomotor responses to anti-IgM and anti-IgD at between 10 ng and 1 microgram/ml. Because this locomotion is activated through the antigen receptor and may simulate a response to antigen, we set out to establish whether this was a chemotactic response using a checkerboard filter assay with a range of concentrations and concentration gradients of anti-IgD. At high concentrations (100 ng/ml to 1 microgram/ml), a chemokinetic response, but no chemotaxis, to anti-IgD was seen. However, in concentration gradients set up at lower concentrations (0-50 ng/ml) a chemotactic response was demonstrable. During the period of culture in anti-IgD at 1 microgram/ml, a progressive loss of surface IgD from the cells was seen, but there was no loss at 10 ng/ml. This receptor loss from the cell surface may account for the lack of chemotactic effect of the anti-IgD at higher concentrations.
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