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Histamine H-1 binding site on human polymorphonuclear leukocytes
Abstract:
Neutrophilic polymorphonuclear leukocytes (PMN) infiltrate the sites of allergic reactions and may respond to histamine, one of the major mediators of allergy. In order to characterize histamine interactions with PMN, the binding of [3H]pyrilamine was studied. Human PMNs bind [3H]pyrilamine in a specific, saturable, and reversible fashion and demonstrate specificity (H-1 antagonists greater than histamine greater than H-2 antagonists) for the competitive binding agents studied. Human PMNs have a homogeneous population of H-1 receptors of moderate affinity (Kd = 52 nM) in large number (265 X 10(3)/cell) which do not demonstrate cooperativity. Thus PMNs attracted to sites of allergic inflammation have H-1 binding sites which may respond to histamine stimulation.
Insights
Human neutrophils (PMN) possess histamine H-1 receptors, crucial for allergic reactions. These receptors bind histamine, influencing the inflammatory response at allergic sites.
Area of Science:
- Immunology
- Allergy Research
- Pharmacology
Background:
- Neutrophilic polymorphonuclear leukocytes (PMN) are key immune cells involved in allergic reactions.
- Histamine is a primary mediator released during allergic responses.
- Understanding histamine's interaction with PMNs is vital for allergy research.
Purpose of the Study:
- To characterize the binding of histamine to human neutrophils.
- To identify the type and characteristics of histamine receptors on PMNs.
Main Methods:
- Utilized [3H]pyrilamine to study histamine binding to human PMNs.
- Performed competitive binding assays with H-1 and H-2 antagonists.
Main Results:
- Human PMNs exhibit specific, saturable, and reversible binding of [3H]pyrilamine.
- Binding demonstrated specificity for H-1 antagonists over histamine and H-2 antagonists.
- Identified a homogeneous population of moderate-affinity H-1 receptors (Kd = 52 nM) on PMNs, numbering approximately 265,000 per cell.
Conclusions:
- Human PMNs possess functional histamine H-1 receptors.
- These H-1 receptors on PMNs may play a significant role in mediating responses to histamine during allergic inflammation.