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The M-antigen in HK and LK sheep red cell membranes
1Department of Physiology & Pharmacology, Duke University, 27706, Durham, North Carolina.
Abstract:
Red cells of all high-potassium-type (HK) sheep and of more than one half of all low-potassium-type (LK) sheep contained the M-antigen and were hemolyzed by iso-immune anti-M antiserum in presence of a guinea pig serum complement. It was characteristic for the hemolysis of HK red cells by the M-antiserum the all HK cells were ultimately hemolyzed at suboptimal antibody concentrations, provided the time of incubation at 37 °C was sufficiently long. Thus, the M-antigen appears to be expressed on all red cells of an individual HK sheep. The M-antibody was absorbed by HK red cells and their membranes with a high affinity, whereas M-negative LK red cells and their membranes did not bind the antibody. The ratio of the number of antibody units absorbed per cell or membrane to the number of antibody units required for lysis approached unity. The amount of antibody absorbed per membrane was unaffected by ouabain in the presence of ATP, Mg(++), Na(+), and K(+). The M-antigen activity depends on the integrity of the red cell membrane and was not detectable after lyophilization of HK membranes or in the membrane protein solubilized by n-butanol. The major M-antibody activity was found among the high molecular weight plasma proteins and may be attributed to the β2 M globulins. Heterogeneity within the antibody fraction cannot be excluded since some hemolytic activity was detected in a chromatographic fraction containing predominantly γ-globulin. The relationship between the M-antigen and the Na(+)-K(+) transport system in sheep red cell membranes is discussed.
Insights
Sheep red blood cells (RBCs) express the M-antigen, which is recognized by specific antibodies. This antigen
Area of Science:
- Immunology
- Biochemistry
- Cell Biology
Background:
- Sheep red blood cells (RBCs) exhibit variations in potassium (K+) transport, categorized as high-potassium (HK) and low-potassium (LK) types.
- The M-antigen is a surface marker found on some sheep RBCs, with its expression potentially linked to membrane properties.
Purpose of the Study:
- To investigate the presence and characteristics of the M-antigen on HK and LK sheep RBCs.
- To determine the nature of the M-antibody and its interaction with sheep RBC membranes.
- To explore the relationship between the M-antigen and the sodium-potassium (Na+-K+) transport system.
Main Methods:
- Hemolysis assays using iso-immune anti-M antiserum and complement.
- Antibody absorption studies with intact RBCs and isolated membranes.
- Analysis of antibody binding affinity and quantity.
- Investigation of M-antigen activity after membrane modification (lyophilization, solubilization).
Main Results:
- The M-antigen is present on all HK sheep RBCs and over half of LK sheep RBCs, leading to hemolysis.
- HK RBCs and their membranes exhibit high affinity for M-antibody, while M-negative LK cells do not bind.
- M-antigen activity requires membrane integrity and is lost upon lyophilization or solubilization.
- M-antibody activity is primarily associated with high molecular weight plasma proteins, potentially β2 M globulins.
Conclusions:
- The M-antigen is a distinct surface marker on sheep RBCs, with differential expression between HK and LK types.
- The M-antigen's interaction with its antibody is specific and dependent on the native structure of the red cell membrane.
- Further research is warranted to elucidate the precise connection between the M-antigen and the Na+-K+ transport system in sheep erythrocytes.
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