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Kell Antigen System

Instructor: Stephanie Gorski

Steph has a PhD in Entomology and teaches college biology and ecology.

The Kell antigen system is an important blood group system. In this lesson we will discuss blood types, specifically the Kell-positive and Kell-negative blood type, and a disease associated with Kell-positive individuals.

Henry VIII

Why couldn't Henry VIII have a son? And why did that make him so angry, to a degree that some have described as psychotic? Recent researchers have suggested that his blood type may be the cause. Specifically, researchers have suggested that he may have had a Kell-positive allele, causing both his bad luck in reproduction and his eventual reputation as a cruel tyrant. Of course, no one in Henry VIII's time knew anything about Kell antigens.

Blood Types

As late as 1900, it was still a mystery why some blood transfusions worked and some didn't. Dr. Karl Landsteiner drew blood from all the members of his staff, mixed the blood together, and found that some people's blood would mix easily while other blood mixtures would clump. This is how he first discovered blood type, and he would later win a Nobel Prize for his discovery.

When we talk about your blood type, we are referring to the shape of molecules called antigens that are capable of eliciting an immune response from your body. The most famous antigens, those causing your ABO blood type, are agglutinogens that reside on the surface of your red blood cells.

Typing is important because if two blood cells have different types, they 'know' that they are not from the same individual and will attack each other as foreign invaders. For instance, you may be familiar with ABO blood typing, and Rh blood typing. If you have type A- blood, you have type A antigens and no (negative) Rh antigens on your blood cells. So if you were to receive a blood transfusion from someone with B+ blood, they would have very different antigens. The transfusion would probably not go well.

Kell blood types describe a very different molecule than the AB molecule or the Rh molecule, but they describe a similar system. The Kell blood type system is highly polymorphic, meaning that there are many different alleles (alternative forms of a gene) - about 25!

The two major codominant alleles, K (Kell-positive) and k (Kell-negative), produce proteins that only differ by a single amino acid. In most places, Kell-negative alleles are more common. Kell proteins are generally found on red blood cells, like agglutinogens. However, small amounts of Kell proteins have also been found on muscle, lymph, and nervous tissues.

The Kell blood system is considered to be the most strongly antigenic besides the Rh system, meaning that only two exposures to Kell-positive cells are enough for Kell-negative individuals to make antibodies to attack Kell-positive cells.

Kell Blood Types and Reproductive Compatibility

Of course, the Kell blood type was not known in Henry VIII's time. It was named for Mrs. Kelleher, a woman whose newborn child was suffering from a blood disease, when it was first identified in 1946.

When a Kell-negative mother has a child with a Kell-positive father, the father can pass on one of two alleles: a Kell-positive allele or a Kell-negative allele. If the child receives a Kell-negative allele, the pregnancy occurs as normal. If the child receives a Kell-positive allele, her body may recognize the developing fetus as a foreign body and attack it. The first Kell-positive child a Kell-negative mother has will often have no complications. But after that, her body will develop antibodies against Kell. Subsequent Kell-positive kids will be attacked by her immune system, and often cause spontaneous abortion.

This is consistent with Henry VIII's reproductive history. Though it was still fairly common for children to die in infancy in those days, most late-stage pregnancies at least led to live births. In contrast, though Henry VIII's partners had at least eleven pregnancies (possibly several more), only four of his children survived infancy. The children who did survive likely inherited their father's recessive Kell-negative allele.

McLeod Syndrome

When he was young, Henry VIII was considered fairly fit, good-looking, and pleasant to be around. But in his late 30's, his health deteriorated. In addition, he seemed to be suffering from emotional disturbances, to put it mildly. Tragically, he executed two of his six wives. He was also known as a deeply paranoid individual who broke England's ties with the Catholic Church over his inability to have a son.

Henry VIII
Henry VIII

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