Human lymphocytes bear membrane receptors for C3b and C3d

Area of Science:

• Immunology
• Cell Biology

Background:

• Human peripheral blood lymphocytes exhibit membrane receptors for antibody and complement-sensitized sheep erythrocytes (EAC43b).
• These lymphocytes also bind to EAC43d, derived from EAC43b treated with C3b inactivator.

Purpose of the Study:

• To investigate the differential binding of complement fragments to human immune cells.
• To explore the potential selective distribution of C3b and C3d receptors on lymphocyte subpopulations.

Main Methods:

• Utilized sheep erythrocytes sensitized with antibody and complement (EAC43b).
• Prepared EAC43d by treating EAC43b with C3b inactivator.
• Analyzed rosette formation inhibition using C3 fragments from trypsin-digested human C3.

Main Results:

• Human lymphocytes bind to both EAC43b and EAC43d.
• Human granulocytes exclusively bind to EAC43b.
• C3 fragments displayed both C3b and C3d sites, inhibiting lymphocyte rosette formation with both EAC types.

Conclusions:

• Suggests the presence of distinct C3b and C3d receptors on human lymphocytes.
• Highlights potential selective distribution of these receptors on normal B lymphocyte subpopulations.
• Raises possibilities regarding receptor distribution on leukemic leukocytes.