Bennett-Goodspeed (Bg) is human leukocyte antigens (HLA) that are extremely rare. Therefore, they are categorized as low-incidence antigens and cause little concern in compatibility during a blood transfusion. However, Bg antigens are not accepted as a blood group system because of their lack of reproducibility and their production of doubtful results when tested in inheritance family studies (Seaman et al., 1967). They are found in immune sera as contaminants, mainly after blood transfusion, and rarely as natural antibodies.
Key Characteristics of Bg Antigens
Since Bg antigens are HLAs, they encode cell surface proteins that are tasked with regulating the body’s immune system. Bg antigens are highly polymorphic, with different alleles that support streamlining an adaptive immune system. HLAs are categorized into MHC Classes I, II, and III, with the first producing peptides from inside the cell, the second one presenting antigens from outside, and the third encoding complement system components (Seaman et al., 1967). Class I has major and minor genes, as A, B, C and E, F, and G, respectively.
Key Characteristics of Bg Antigens Cont’d
The Bg antigens have features that allow them to be used by the immune system to distinguish themselves from foreign cells. Pathogens from infectious diseases are detected by MHC Class II through phagocytosis and displayed to the CD4+ helper T-cells for elimination. MHC Class I follows a similar process to present invading cells from inside to CD8+ helper T-cells. Specific HLA antigens are linked to autoimmune disorders such as celiac disease, type I diabetes, and rheumatoid arthritis (Seaman et al., 1967). During organ transplants, Bg antigens may treat new tissue as invaders, leading to rejection. Bg antigens lack straightforward inheritance when tested in family studies, but there is evidence of a Mendelian pattern. In addition, they are only partially developed at birth and in the first months of life, gaining adult standards after the first birthday.
Bg antigens are tested in an autoanalyzer circuit that utilizes cell suspensions, anti-sera, bromelin, and PVP. The process begins with preparing the cell suspensions by mixing and adding a reagent containing P.V.P, anti-serum, bromelin, and a wetting agent. The resulting suspension is passed through a delay coil for 45 minutes, then added saline in large amounts to disband rouleaux (Seaman et al., 1967). Cells then undergo settling and decanting twice to achieve the required sedimentation. The cells that remain go through lysing with water and pass through the colorimeter recorder.
Titration and antiglobulin are other testing methods that are manual in nature. The antiglobulin technique is less accurate than the autoanalyzer, while titration is more accurate than the other two methods. Therefore, titration is preferred or utilized with cells that had a 30-40% decrease in optical density, as they cannot be categorized as Bg positive or negative (Seaman et al., 1967). The weakest cells also react better during titration as the dilution ratio is hugely increased. Cross-reactivity is also tested in the autoanalyzer and through titration by changing absorption volume and dilution rates.
Incidence in the General Population
Bg antigens are extremely rare and have low incidence rates in the general population. Mostly, they are found in transfused persons but can occur in natural antibodies (Seaman et al., 1967). In addition, some individuals have Bg antigens after organ transplants. Therefore, they are not considered clinically significant due to the low incidence and rare occurrence.
Some interesting facts about Bg antigens include their discovery and clinical features. For example, their rareness renders them clinically insignificant and not widely studied. Although discovered after the main blood group systems were known, they were not recognized because of their unsuitability for phenotyping. Each Bg antigen is correlated with a specific HLA with Bga correlating with HLA-B7, Bgb with HLA-B18, and Bgc with HLA-A28 (Seaman et al., 1967). This link with HLA was made in 1975 but is studied today (Seaman et al., 1967). In addition, scientists have found Bg antigens to occur in some pregnant mothers. Unlike the main blood group systems, Bg antigens are only manifested in mature red blood cells, detected as partially developed in infants under one year old.
The Bg antigens are not recognized as blood group systems due to lack of reproducibility, phenotyping not applicable to red blood cells, and unclear results in family studies. They only occur in mature red blood cells in children over one-year-old. They can be tested in cells using the manual antiglobulin method, automated autoanalyzer tool, or titrations. Scientists linked the Bg antigens to HLAs in 1975, where Bga correlates with HLA-B7, Bgb with HLA-B18, and Bgc with HLA-A28. They are not clinically relevant due to their low incidence rates and occurrence in red blood cells. They are mostly found in people who have completed blood transfusions, organ transplants, and sometimes in pregnancy.
Seaman, M. J., Benson, R., Jones, M. N., Morton, J. A., & Pickles, M. M. (1967). The reactions of the Bennett—Goodspeed group of antibodies tested with the AutoAnalyzer. British Journal of Haematology, 13(s1), 464–473. Web.