What are the characteristics of O (O) Rh (Rhesus) positive blood type?

Characteristics of O Rh+ Blood Type

O Rh+ (O positive) is the most common blood type, characterized by the absence of A and B antigens on red blood cells and the presence of the Rhesus D antigen. This blood type combines the O blood group from the ABO system with the positive Rhesus factor.

ABO System Characteristics

• O blood type is defined by the absence of both A and B antigens on red blood cell surfaces, while having anti-A and anti-B antibodies in the plasma 1
• O is one of the four main blood groups in the ABO system (A, B, AB, and O) with a frequency of approximately 34.22% in studied populations 1
• People with O blood type can donate red blood cells to recipients of any ABO blood type (A, B, AB, and O), making them universal red cell donors 2

Rhesus System Characteristics

• The Rh+ designation indicates the presence of the D antigen on red blood cells 3
• The D antigen is the most immunogenic of the Rh system antigens, capable of triggering strong immune responses when transfused to Rh-negative individuals 2
• Approximately 85.79% of people are Rh positive (have the D antigen) 1
• The Rh system consists of multiple antigens beyond D, including C, c, E, and e, which are also important in transfusion medicine 4

Clinical Significance

• O Rh+ individuals can receive blood only from O Rh+ or O Rh- donors 2
• O Rh+ blood is commonly used in emergency situations when a patient's blood type is unknown, as it poses less risk than using type-specific blood without proper cross-matching 2
• The risk of inducing anti-D antibodies when giving O Rh+ blood to emergency patients with unknown blood type is relatively low (3-6%) 2

Molecular Characteristics

• The Rh antigens are carried by non-glycosylated hydrophobic transmembrane proteins of 30-32 kDa 3
• The RhD protein has an apparent molecular weight of 28,000-33,000 5
• The RhD protein is encoded by the RHD gene located on chromosome 1p34-p36 3
• The Rh proteins have 12 transmembrane domains with short connecting loops, with most of the protein residing within the red cell membrane 3

Transfusion Considerations

• For patients requiring chronic transfusions, matching beyond just ABO and RhD is recommended to prevent alloimmunization 4
• Extended matching for other Rh antigens (C, c, E, e) and K antigen is particularly important for patients with conditions requiring multiple transfusions 4
• Despite prophylactic matching for Rh antigens, alloimmunization can still occur due to RH gene variants, especially in diverse populations 6
• In emergency situations, O Rh+ blood can be safely used for most patients, helping to preserve the limited supply of O Rh- blood 2

Prevalence and Distribution

• O Rh+ is the most common blood type in many populations worldwide 1
• The frequency of blood group antigens varies among different ethnic populations 1
• The most common Rh phenotype is DCcee (32.7%), while the rarest is DCCEE (0.003%) 1

Genetic Aspects

• The Rh proteins are erythroid-specific and share no sequence homology with any other known proteins 3
• The RHD and RHCE genes encoding the Rh proteins likely derived from duplication of a common ancestral gene 3
• Gene conversion appears to be the principal mechanism responsible for polymorphism and gene diversity in the RH system 3
• RH genetic diversity is an important factor in alloimmunization risk, particularly in certain patient populations 4