Hello!!
This week I will be discussing how tests determine whether you have Covid-19 based on your antibody response. There are two classes of antibodies that I will be discussing today. First there is the IgM antibody. Your body produces this antibody class first during a primary response. When it binds to the antigen, it activates the complement system. The second antibody class is the IgG molecule. It is the most abundant class in the blood and tissue fluids. This molecule binds to the antigen and sends signals to guide phagocytosis. This molecule also activates the complement system. This molecule is special because it is the only one that can provide protection to a baby because it can be transported across the placenta. It provides the longest term protection because of its long half life which can protect the baby for several months after its born.
So how is this useful in Covid-19 testing? According to an article in MedicineNet, a total detection of three lines is possible. There is a quality control line, an IgM line, and an IgG line. You have a negative result if only the quality control line appears and there is no G and M line. You have a positive if both the quality control line (C) and the IgM (M) line appears. You have a positive if the IgG and C line appear. You have a positive if all three C, M, and G lines appear. If the immunoglobulin tests are all negative, that means you have not been recently exposed to the virus. If the M line appears, that means you are in the early stages of the virus infection. If both lines appear, that means you are in the middle stages of infection. If only the G line appears, that means that the person is either over the infection or in its last stages. This makes sense right? Because IgG has a long half life, it stays in your system longer than IgA. IgA is the first antibody class that’s produced during infection so if it’s not in your system and IgG is, you have had Covid-19 for a while. This is really important to understand because people who are IgG positive are contagious and could potentially continue to infect others. This is also cool because they may be growing an immune response.
I know that was a lot to grasp, but it is really cool stuff to know. Unfortunately, not everyone can be tested. According to NPR, there is a severe shortage for test kits in the US. The president is insistent that the situation is improving, but in reality: we do not know. I personally have had friends tell me that their family members may have Covid-19, but their healthcare providers refused to test them due to the lack of resources. If we do not know the true statistics for who does and does not have the virus, we can’t make overstated claims on the current situation. I pray that everyone reading (and others too(: ) are safe and healthy during this time.
Also Happy Easter!!
Microbiology with Alicia 