Related Experiment Videos
Human B lymphocytes express the p75 component of the interleukin 2 receptor
C G Begley1, J D Burton, M Tsudo
1Metabolism Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Insights
Human B lymphocytes possess a p75 interleukin-2 (IL-2) receptor. Malignant B cells and normal B cells express this molecule, with IL-2 inducing high-affinity receptors on normal and CLL B cells.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The interleukin-2 (IL-2) receptor plays a crucial role in immune responses.
- B lymphocytes are key players in humoral immunity.
- Understanding IL-2 receptor expression on B cells is vital for comprehending immune regulation and B cell malignancies.
Purpose of the Study:
- To investigate the characteristics of the IL-2 receptor on normal and malignant human B lymphocytes.
- To determine the presence and affinity of IL-2 binding sites on B cells.
- To examine the modulation of IL-2 receptor expression upon IL-2 stimulation.
Main Methods:
- Purification of human B lymphocytes from normal donors and patients with hairy cell leukemia (HCL) and chronic lymphocytic leukemia (CLL).
- Binding assays using 125I-labeled IL-2 to quantify IL-2 binding sites and determine dissociation constants (Kd).
- Receptor cross-linking experiments to identify the molecular weight of IL-2 binding molecules.
- Stimulation of B lymphocytes with IL-2 and Staphylococcus aureus Cowan I to assess receptor induction.
Main Results:
- Both normal and malignant B lymphocytes (HCL, CLL) express a 70-75,000 mol. wt (p75) IL-2 binding molecule.
- Normal B lymphocytes exhibit approximately 1100 p75 binding sites per cell with a Kd of 1.7 nM.
- HCL samples showed a small number of high-affinity sites and numerous low-affinity p55 Tac binding sites.
- IL-2 stimulation induced p55 Tac expression and high-affinity IL-2 receptors on normal and CLL B lymphocytes, similar to stimulation with Staphylococcus aureus Cowan I.
Conclusions:
- Human B lymphocytes express the p75 IL-2 binding molecule.
- Malignant B cells in HCL and CLL also express the p75 IL-2 receptor.
- IL-2 can induce the formation of high-affinity IL-2 receptors on normal and CLL B lymphocytes, suggesting a role for IL-2 in B cell activation and function.
Abstract:
The nature of the interleukin 2 (IL-2) receptor on purified human B lymphocytes was examined. Both normal and malignant cells showed evidence of a 70-75,000 mol. wt (p75) IL-2 binding molecule as assessed by 125I-labeled IL-2 binding and receptor cross-linking. On normal, Tac-negative B lymphocytes the estimated number of p75 binding sites was 1100 per cell and the dissociation constant (Kd) was 1.7 nM. Consistent with this, cross-linking experiments demonstrated the presence of an IL-2 binding molecule of 70-75,000 mol. wt. Purified B cells from patients with hairy cell leukemia and chronic lymphocytic leukemia (CLL) also expressed the p75 IL-2 binding molecule. In the HCL samples, a small number of high-affinity IL-2 binding sites were detected (27-90) while the majority of binding sites (2100-10,800) were typical of low-affinity p55 Tac binding. IL-2 added to the purified normal and CLL B lymphocytes led to the induction of p55 Tac expression and the generation of high-affinity IL-2 receptors. This response to IL-2 was equivalent to the response observed when normal B lymphocytes were stimulated by Staphylococcus aureus Cowan I.