Transcript: Clonal Deletion Theory of Immunity
As I described, the clonal selection theory of immunity suggests that we start out able to fend off basically every cellular structure in the known universe because we have a billion different types of antibody producing B cells, each capable of recognizing a different molecular signature. Why then do we tend not to attack ourselves? Because before we’re even born we kill off each and every B cell that recognizes us. It’s called clonal deletion, the killing off of forbidden clones. That’s what our thymus gland is for. When we’re still a fetus, our body lines up all our immune cells, our B cells, our T cells, holds up a picture of our self and asks them one by one: "do you recognize this person." And if any of our immune cells says yes, they’re shot in the head. Killed on the spot, death by apopotosis and good riddance. Turns out this process of clonal deletion, ridding our bodies of self-recognizing immune cells happens throughout our lives, mostly in our bone marrow. If you remember, though, as I talked about before, IGF-1, the cancer-promoting growth hormone boosted by animal protein consumption prevents apoptosis, prevents our body’s killing of cells it wants to get rid—that’s why IGF-1 levels are linked to cancer. So “It is of great interest to determine whether IGF might contribute to the inappropriate survival of lymphocytes in autoimmune or inflammatory conditions.” Maybe that’s why people who eat plant-based diets appear protected from autoimmune diseases, explaining, for example, the “extraordinary rarity of most autoimmune diseases among sub-Saharan rural blacks following a traditional vegan lifestyle.” Before they changed their diet, evidently “not a single case of MS had been diagnosed among a population of 15 million.’”
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ashley Rhinehart, RN.
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