Question

How can the sperm cells of a man be attacked by his T cells?

Short answer

T cells can attack sperm cells if the immune privilege of the testes is disrupted due to trauma, an infection or surgery. Alternatively, an autoimmune response can mistakenly cause the body to attack its own sperm cells.

Step-by-step solution

Understanding T cells

T cells, also known as T lymphocytes, are a type of white blood cell that is a key part of the immune system. They identify and kill infected cells as well as coordinate the immune response.

Understanding the immune privilege of testes

Certain areas in the body like the eyes, brain and testes are considered 'immune privileged' sites. This means that the typical immune response to foreign cells is dampened or prevented altogether to avoid potential damage to these sensitive areas. In the case of the testes, this helps to protect sperm from being attacked by the immune system.

Scenarios where T cells attack sperm cells

Despite the immune privilege, there are circumstances that can lead to sperm cells being attacked by T cells. One potential scenario is if the immune privilege of the testes is disrupted due to trauma, infection or surgery. In such cases, the T cells can recognize sperm cells as foreign bodies and attack them. Another scenario could be an autoimmune response, where the body mistakenly begins to attack its own cells, in this case, sperm cells.

Key concepts

T cells

T cells are vital components of the immune system and play a crucial role in protecting the body against pathogens and disease.

Known scientifically as T lymphocytes, these cells originate in the bone marrow and mature in the thymus, which is how they get their 'T' designation. There are several types of T cells, each with different functions. For example, 'helper T cells' assist other white blood cells in immunologic processes, including the activation of B cells to secrete antibodies and macrophages to destroy ingested microbes. 'Killer T cells,' on the other hand, are involved in directly attacking cells that have been infected by viruses or have become cancerous.

A critical aspect of T cells' function is their ability to distinguish between the body's own cells and foreign cells. This self/non-self recognition is essential to the immune system's ability to defend against pathogens without attacking the body itself. However, this mechanism can sometimes go awry, leading to autoimmune responses where T cells target the body's own tissues.

Immune Response

The immune response is the body's defensive reaction to foreign substances, such as pathogens or vaccines, and sometimes its own cells in the case of autoimmune diseases.

When a pathogen invades the body, the immune system responds in a sophisticated and coordinated manner. Initially, the innate immune response, which includes physical barriers like the skin and mucous membranes, as well as cells like phagocytes and natural killer cells, acts to impede the invader's progress. If these are unable to contain the threat, the adaptive immune response is triggered.

This response involves T cells and B cells, which have specific receptors for antigens presented by the invading pathogen. T cells, particularly, play a pivotal role by directly killing infected cells or by helping B cells to produce antibodies. The immune system's ability to remember these antigens leads to a faster and more effective response upon subsequent exposures, which is the basis of immunity.

Autoimmune Response

An autoimmune response occurs when the immune system mistakenly identifies the body's own cells as foreign invaders and attacks them. This can result in various autoimmune diseases, depending on the type of tissue that is being targeted.

The mechanisms leading to autoimmune responses are complex and not fully understood. Genetic and environmental factors are believed to contribute to the loss of immune tolerance, where T cells start reacting against the body's own proteins. Some theories suggest that infections can trigger an autoimmune response due to a process known as molecular mimicry, where the immune system confuses similar looking proteins on pathogens with those in the host organism.

Autoimmune responses can be systemic, affecting multiple organs, or organ-specific, like in Type 1 diabetes where pancreatic beta cells are destroyed. Treatment for autoimmune diseases often involves immunosuppression to reduce the immune system's activity against the body's own cells.