Secretors and Non-Secretors, Blood Groups Antigens, and Antibodies. Immunologic Involvement against Invaders.

Secretors and Non-Secretors

The world population is divided into two different groups referring to blood group systems, secretors, and non-secretors.

Maybe a connection on how the COVID-19 coronavirus is affecting the global population.

I was always intrigued about the concept of secretor and non-secretor since I apprehended from Dr. Peter D’Adamo and I am using his theories now to develop a questionnaire and potential brainstorming around a concept that probably for himself does not make any sense in this case.

Blood Groups Analysis

Source: “Eat Right 4 Your Type” “Blood Type Encyclopedia” Dr. Peter J. D’Adamo

In the ABO system each blood group has a different antigen with its own structure and blood groups are named based on this characteristic.

Blood type A has an A antigen on its red blood cells, group B a B antigen, group AB has both A and B antigens, blood type O has  the H antigen which is not really an antigen and because of this is referred as group zero in Europe.

Blood groups under the chemical structure are made of long chains of repeating sugars that end with a sugar called fucose, the simplest of the blood group antigens, O or H; this antigen also is the platform for the other blood groups and which are determined by our genetics.

For example, blood group A is capable to produce an enzyme that converts the H antigen into the A antigen, group B in B, group AB both the enzymes, while group O does not produce enzymes for cannot convert its H in any other antigen.

Blood group A is made of the O sugar, fucose and another sugar, N-acetyl galactosamine by its end. Blood group B by fucose and D-galactosamine at its end. Blood group AB from fucose and both the other sugars, N-acetyl-galactosamine and D-galactosamine.  Blood group O only from fucose.

Immunologic Involvement of Blood Groups

When the immune system perceives a potential invader creates antibodies against that antigen, these antibodies are made from the immune cells, and each is specifically designed to identify and attach to the specific shape of an antigen.

Antibodies have a constant portion to which the cells of the immune system can bind and a variable portion made normally of two arms that can be adjusted to the shape and size of the antigen and that together the constant portion gives to the antibody the shape of a Y.

If there is a constant fight between antigens and antibodies as during the course of a disease and change or mutation of an antigen the antibody will not recognize, and the immune system will respond increasing the number and type of antibodies.

Blood groups produce antibodies to other blood group antigens, the reason for transfusions need be done from same blood types or from a type which does not have antigens and so antibodies against, as blood type O, the universal donor.

Antibodies against other blood groups, or anti-blood group antibodies are Ig M, and are the most potent in our immune system because of their shape, they actually have a star configuration because the variable portion is made of 5 arms, fort his reason they can attach to more antigens; this is what causes agglutination, and the reason why these antibodies are named hemagglutinins because they agglutinate antigens on blood red cells or any other microorganism that enters in our system.

This powerful ability of the hemagglutinins to agglutinate can be detected on a glass slide with naked eyes, without microscope, and it is the most common way of identifying blood groups in laboratory.

Most antibodies require a stimulation to be produced as a vaccination or an infection, the blood group antibodies are produced automatically from birth and reach the adult levels by four months as result of introduction of food or microbes of a different blood group.

When intruders of any type are agglutinated from these antibodies they stick together and clump and this make easier to be detected from the other components of the immune system as the complement, for example, which detects immune-complexes, and to be eliminated.    

When this hemagglutination occurs within blood groups due to a wrong blood transfusion the results are those typical of a mistaken blood transfusion, and pretty dangerous, as anaphylactic shock, for example.

Principles of Blood Groups Transfusion

Referring to the ABO system and ways a transfusion can happen, blood type A has antibodies against  blood type B for having the A antigen, for this reason can receive blood only from type A and O, while type B has anti-A, for can only receive from B and O, AB has both the antigens and not antibodies against, and for this reason can receive from each other type, and is the universal acceptor, none of the groups has instead antibodies against blood group O because this one does not have antigens and this is why blood group O is the universal donor.

The Lewis System

Secretors and non-secretors are characterized by the Lewis system of blood groups, secretors are the 80% of population and those who carry the blood type antigens in their secrets, like saliva and mucus and that for this reason have a  better protection and stronger immune system, non-secretors the 20%, instead, do not carry blood type antigens in their secrets and therefore have a weaker immune system and lesser protection.

The Lewis system of blood groups, by the doctor’s definition can be performed on secrets for being the antigens in the secrets, the most common way is the test on saliva for the presence of the ABH antigen, if this antigen is present the person is secretor, if not, non-secretor; or can be also done on blood using the Lewis blood group system.

Being secretor or non-secretor is independent from the ABO blood group and it is controlled by a different gene; this is defined as ABH secretor system, and it means that a type A or B or O or AB can be either secretor or non- secretor

In this system two possible antigens can be produced, Lewis-a and Lewis-b, with no relation with the A and B blood groups. People can type as:

Lewis-(a-b+), or Le(a-b+) = secretor

Lewis-(a+b-), or Le(a+b-) = non-secretor

Lewis (a-b-), or Le(a-b-) = Lewis negative or double negative (secretor or non-secretor)

The reason for there are Lewis negative individuals is due to the fact that a small number of individuals (6% of white population and 16% of the black population) are genetically not capable to manufacture Lewis-a since the birth.

For this small percentage of people, the Lewis system cannot be used for definition of secretor status but based on the doctor’s experience they can be included with non-secretor since they share many of the health problems and serious consequences.

For example, non-secretors are more prone to general inflammation and autoimmune diseases than secretors, to both types of diabetes and metabolic problems, heart disease, urinary infections, cancer, and immunodeficiency.

I was wondering if the differentiation in secretor and non-secretor has to do with the fact that the 20% of the global population results in that was supposed to be more hit from the virus based on the statistics of the health organizations, while the majority correspondent to the 80% should be the one with less severity of symptoms and course of the disease or even asymptomatic.

But is this what has been happening or the statistics are different? I leave this conclusion and evaluation to the experts with the hope that can be found some kind of connections with this typization among secretors and non-secretors and the way the population are hit from the virus of the pandemic.

Blood Groups and Connections with COVID-19

In regard instead of the connection among blood groups and the virus based on what has been observed in China where the major number of critical cases were blood type A,  Dr. D’Adamo ‘s conclusion has been of not too much importance because of other factors that influence the risks and process of this disease and its complications as the comorbidity for example and which could be due, (I am personally adding), to the distinction between secretor and non-secretors?

Here is a statement from his own article: “COVID-19: ABO BLOOD TYPE”

This is the link:

From a citation from this article: In a study published in 2008 in a journal of Glycobiology was observed that the property of the spike proteins of coronaviruses to adhere to cells expressing the enzyme ACE-2 was inhibited either from monoclonal than from natural human antibodies.

“This indicated that these antibodies may block the interaction between the virus and its receptor, thereby providing protection. They concluded that ‘the ABO polymorphism could contribute to substantially reduce the virus transmission, affecting both the number of infected individuals and the kinetics of the epidemic.”

Dr. D’Adamo’s Statement:

“There is a long evidence-based history that linking the ABO blood types (A, B, AB and O) with specific differences in susceptibility to a wide range of infectious illnesses, including smallpox, plague, cholera and influenza. Although most speculation calls research to identify some aspect of the difference between the cell antigens that characterize the physical manifestation of ABO blood type, it is much more likely that the cause behind the blood type differences lay instead with the opposing blood group antibodies and not the antigens”.

Reconsidering instead the classification secretors, non-secretors, if really this virus- having an A-type configuration- can recognize A-type structures as blood groups A, for example, non-secretors, blood type-A people with not antigens in their secrets should not be recognized easily by the virus. It appears very controversial and ambiguous, just a hypothesis.

Thanks for Reading.

Mariarosaria M.

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