How does the body develop immunity to an infection?

Dear Doc,
How does the body develop immunity to infection? Then, what is genome-sequencing,  stem-cell research and mutation? 

Dear reader,

Thank you for the questions.

Immunity: The immune system is a system of cells and chemicals that identify and tolerate what belongs to self and identifies and rejects foreign invaders. 

When the body encounters a foreign invader, in this case an infection, the cells of the immune system identify it as an intruder and activates a process that results in formation of antibodies that destroy or neutralise the invader. The antibodies produced are specific to that intruder. For instance, if you got influenza, the body will make antibodies against that specific type of influenza. In addition to making antibodies, the immune system has cells that memorise the invader, and continue to circulate in your body for a long time, and will be activated in case you encounter the invader again, and quickly neutralise it. You can get active immunity by directly encountering the invader, or by being vaccinated with a piece of the invader (or a killed or weakened version) so as to trigger the immune response in the body. You can also get passive immunity by being given the antibodies to a specific invader through immunoglobulin treatments or through mother-to-child transmission of antibodies. Passive immunity is useful in the short term, but it doesn’t last long.

Genome-sequencing: The gene is the basic unit of heredity found in a long molecule called DNA (Deoxy Ribonucleic Acid) or RNA (Ribonucleic Acid) for RNA viruses. 

DNA or RNA is made up of four building blocks or bases – Adenine (A), Cytosine (C), Guanine (G) and Thymine (T). The order or sequence in which these bases are arranged is what gives genetic instructions for functioning, growth and reproduction. Genomic sequencing means determining the order of the four bases that make up a DNA molecule. This is what is checked, for example, to identify different types of the Covid-19 virus

Mutation: This is a change in the sequence of the DNA bases of an organism. This can happen when a mistake occurs as DNA and is copied during cell division/multiplication or as an effect of exposure to chemicals or radiation or viral infection.

Stem-cell research: All human beings start out as one cell called a zygote, or a fertilised egg. This cell then divides into two, then into four, into eight... The initial cells have the capacity to become any type of cell. As they continue to divide, the cells change or “differentiate” to perform specific functions in the body such as nerve cells, red blood cells and muscle cells. Stem cells are the cells that have not yet differentiated or specialised and still have the potential to divide and form more stem cells, or form specialised cells. Stem cell research is research on stem cells to treat and understand diseases because stem cells can be grown in a laboratory and be used to replace damaged tissues or correct parts of organs that don’t work well; to research diseases and to test new drugs. The stem cells can be gotten from adult tissues, from umbilical cord blood and amniotic fluid, and from human embryos, three to five days after fertilisation during the IVF (In-vitro fertilisation) process. 

Several eggs are fertilised in the laboratory and two or three are then implanted into the woman, and the rest of the embryos are discarded. Stem cells are harvested from the embryos that were to be discarded. This source of stem cells is the most common and the source of much controversy.

I am 30 years old. Keloids have grown all over my chest. On a hot day they are itchy. Should I be worried?

Dear reader,

Keloids are an overgrowth of scar tissue. When there is an injury or infection on the skin, scar tissue forms to protect the area and help with healing. A keloid may be reddish or brown in colour, it may be itchy, and it may grow over time. You can have keloids forming where there is a rash, cut, burn or even an injection site. On the chest, the keloids may also be the result of acne that many teenagers or young adults develop on the face and chest. You are more likely to develop keloids if one or both of your parents have it.

Keloids are usually not dangerous. If the keloids continue growing or if you want them removed, visit a skin specialist (dermatologist). After examination, a test may be done to check for other diseases. Treatment may involve steroids, cryotherapy and laser or radiation treatments.

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