Blood donation is something a lot of people don’t think about an awful lot. We see the adverts, the social media, and even hear about it on the radio, but unfortunately many of those who are eligible to donate don’t do so. Blood is something that we’d expect to be there for us, and for our loved ones, if we’re unfortunate enough to find ourselves in the situation where we really need it. This world blood donor day, 14th June 2014, we’d like to tell you about about blood and blood groups, and hopefully encourage you to give (and give as often as you can!).
Summer is an exciting time of year – the weather is a little nicer, and we’re much more inclined to spend our days reclining in the sun (when it’s around that is!), than popping into our local blood donation centre. Unfortunately, this means that blood stocks risk running low. The national blood service rely entirely upon the general public, whose donations save many lives across the country every single day. Most of you will know that you can’t just give people any old blood. Once donated, blood is thoroughly tested for blood-borne infection like HIV, hepatitis and HTLV (human T-lymphotropic virus). This prevents the risk of blood transfusion recipients becoming infected from the donor blood. Blood is also typed – many of you will know your own blood type, but not so many of you might know exactly what that means. Generally there are around 8 blood groups – O, A, B and AB, with the possibility of each being either rhesus positive or rhesus negative. These letters give basic information about the blood and allow donors and recipients to be paired together.
Being group A means that your red blood cells have ‘group A antigens’. Antigens are simply molecular markers on the surface of cells that can be recognised by the immune system. Group B means you have B antigens, group AB means you have both A and B antigens, and group O means you have neither A nor B antigens on your red blood cells. Group A patients have ‘group B antibodies’ in their blood. These group B antibodies would bind to the B antigens on the blood cells of a group B patient, leading to blood coagulation in the patient which can be life-threatening. Group B patients have group A antibodies, group O patients have both A and B antibodies, and group AB have neither A nor B antibodies. (confused? See the table below!)
|Blood Group A||Blood Group B||Blood Group AB||Blood Group O|
|Antigens on Red Blood Cells||A||B||A and B||Neither A nor B|
|Antibodies in Blood||B||A||Neither A nor B||A and B|
So blood with particular antigens cannot be given to those recipients whose blood contains antibodies against the antigens. For example, a group A donor (with A antigens) cannot give blood to a group O recipient, as the group O patient’s group A antibodies would react against the A antigens. The rhesus positive or rhesus negative part simply resembles another antigen. Similarly to the ABO system, being rhesus negative (Rh –) means you have no rhesus antigens, and therefore a rhesus positive patient could receive their blood without a reaction to it.
Putting this info together with the ABO system means that an ‘O Rh–’ person could give blood to any person, without fear of a reaction with the recipient’s antibodies, and so this blood type is particularly useful. On the other hand, ‘O Rh–’ patients can only receive blood from ‘O Rh–’ donors, as the recipient has antibodies against A, B and rhesus antigens. There’s a diagram below to explain who can give blood to whom! Use it alongside the table above to work it all out – it can get a little confusing! You know you really understand it when you explain why ‘O Rh-’ donors can give to anyone, and why ‘AB Rh+’ can only give to other ‘AB Rh+’ people! We hope this info on the science behind blood donation has encouraged you to consider giving blood. If you’re already a donor then THANK YOU and please continue to give as often as you can. If you’re not a blood donor, then please do consider signing up.
There’s information on the donation process, where you can give, and how to sign up on the NHS Blood and Transplant Service website.
Storry JR, & Olsson ML (2009). The ABO blood group system revisited: a review and update. Immunohematology / American Red Cross, 25 (2), 48-59 PMID:19927620
Image credit: https://www.flickr.com/photos/wellcomeimages/5814816052/?rb=1