The Human Immune System 101: The Overactive Immune System
Foreword:
The immune system is one of the most complex, nuanced biological systems that function to keep the human race alive each and every day. It is both specific and broad, lifelong, and short-term, inherited and acquired, all at the same time. While it defends against deadly threats such as bacteria and viruses, defects in the immune system can be just as fatal. The Immune System 101 articles describe how this contradictory system works and will summarize the variety of functions of the immune system, its importance, and its potential failings in six different articles.
1. The Human Immune System 101: Innate Immunity
2. The Human Immune System 101: Adaptive Immunity
3. The Human Immune System 101: Bacterial & Viral Defenses Against the Immune System
4. The Human Immune System 101: The Overactive Immune System
5. The Human Immune System 101: The Underactive Immune System
6. The Human Immune System 101: The Immune System and Cancer
An overactive immune system may seem like a good thing, even a great thing to have. However, it can be detrimental to one’s health. Autoimmune diseases occur when the immune system fails to recognize and differentiate self vs. non-self-tissue and immune cells, instead of attacking and killing foreign pathogens, target one’s own healthy tissue resulting in an autoimmune disease (Orbital, 2022). There are several different autoimmune diseases, some of which involve multiple organ systems and some of which involve only one system or cell type. These disorders include systemic lupus erythematosus (lupus), type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and a multitude of others (Orbital, 2022).
Figure 1: Autoimmune Symptoms
Systemic Lupus Erythematosus
Systemic lupus erythematosus—or more commonly known simply as lupus or SLE—is a common autoimmune disease that at least five million people worldwide suffer from, according to the Lupus Foundation of America (Unknown, Lupus Foundation of America, 2019). SLE “is a chronic autoimmune disease characterized by the production of autoantibodies specific for components of the cell nucleus and that causes damage to body tissues and organs,” (Arneth, 2019, p. 1). An important aspect of the onset of the disease deals with tolerance: the immune system's ability to distinguish between self and foreign tissue. During the production of antibodies and the B cells that release those antibodies, the antibodies are typically tested for reactivity and tolerance against self-cells. However, testing for self-tolerance that occurs in the bone marrow is not fail-proof and in patients with autoimmune disorders, self-reactive B cells exit the bone marrow despite checkpoints.
At this stage of immature B cell development, the cell-surface antibody can bind antigens. In the bone marrow microenvironment in which immature B cells emerge, antigens that engage the BCR (B cell receptor) will almost always be self-antigens, which makes regulation at this stage essential...These processes are collectively known as central tolerance. (Nemazee, 2017, p. 281).
In a healthy individual, during central tolerance, B cells that react with self-antigens in the bone marrow microenvironment undergo