APC (Antigen-Presenting Cell): These are immune cells like dendritic cells, macrophages, and B cells that act as "messengers." They detect harmful invaders, process parts of them (called antigens), and present these pieces on their surface to T cells, effectively showing them what to target.

MHC (Major Histocompatibility Complex): MHC molecules are like display stands on the surface of APCs. They hold and present the antigen fragments to T cells. There are different classes of MHC; for CD4 T cells, it's usually MHC class II molecules that present the antigen.

Proinflammatory cytokine: Proinflammatory cytokine release and bacterial antigen presence trigger the elevated synthesis of MHC-II molecules to maximize the presentation of foreign antigens for an efficient CD4+ T cell response. High IFN-γ levels increase the number of MHC-II molecules on professional and nonprofessional APCs, thereby altering the composition of the MHC peptidome in the inflammatory area

Costimulatory molecules: Co-stimulation is a secondary signal which immune cells rely on to activate an immune response in the presence of an antigen-presenting cell. During the activation of lymphocytes, co-stimulation is often crucial to the development of an effective immune response. Co-stimulation is required in addition to the antigen-specific signal from their antigen receptors. APCs, activated in pathogenic conditions, express an increased number of costimulatory molecules

Target Cell: This is a cell in your body that is infected by a virus or has become abnormal (like a cancer cell). The immune system aims to identify and eliminate these target cells to keep you healthy.

MHC (Major Histocompatibility Complex): These are special molecules found on the surface of almost all your cells. They display small pieces of proteins from inside the cell. If a cell is infected or abnormal, MHC molecules show pieces of these problematic proteins to immune cells, acting like a “red flag” to alert the immune system.

B Cell: B cells are a type of white blood cell that helps protect your body from infections. Their special job is to recognize harmful invaders like bacteria and viruses and help your body fight them.

BCR (B Cell Receptor): This is a protein found on the surface of each B cell. It acts like a unique "antenna" that can recognize and bind to specific parts of a pathogen (called antigens). This helps the B cell know exactly what to target.

Antibody: Antibodies are special Y-shaped proteins made by B cells. They recognize and bind to specific harmful substances, called antigens, like bacteria or viruses. By sticking to these invaders, antibodies help neutralize them or mark them for destruction.

Antigen: An antigen is any substance that the immune system recognizes as foreign or dangerous. This can be parts of bacteria, viruses, or other pathogens. Antigens are what antibodies and immune cells "look out for" to protect your body.

CD8: CD8 is a protein found on the surface of a special group of immune cells called cytotoxic T cells. These cells help protect your body by finding and killing infected or abnormal cells, like those infected by viruses or cancer cells.

Granzyme: Granzymes are powerful enzymes released by cytotoxic T cells. Once these enzymes enter a target cell, they trigger processes that lead to the cell's self-destruction, helping to eliminate infected or harmful cells safely.

TSH (Thyroid Stimulating Hormone) is a hormone produced by the pituitary gland in your brain. Its main job is to tell your thyroid gland to make thyroid hormones. Think of TSH as a friendly messenger encouraging your thyroid to work properly.

TSHR (Thyroid Stimulating Hormone Receptor) is like a special "lock" on the thyroid gland that fits the TSH "key." When TSH binds to TSHR, it signals the thyroid gland to produce and release thyroid hormones. This interaction helps keep your body's metabolism running smoothly.

TSHR (Thyroid Stimulating Hormone Receptor)

• Normally, TSHR is found mainly on thyroid cells, where it helps regulate thyroid hormone production.
• In TED, TSHR is also found on orbital fibroblasts (cells around the eyes).
• Autoantibodies from the immune system can mistakenly target TSHR on these orbital fibroblasts.
• This abnormal activation leads to fibroblast proliferation (growth) and production of substances that cause tissue swelling and inflammation behind the eyes.

IGF1R (Insulin-like Growth Factor 1 Receptor)

• IGF1R is present on orbital fibroblasts as well.
• Research shows that in TED, IGF1R forms a complex with TSHR, and both receptors can be activated by autoantibodies.
• Activation of IGF1R contributes to signaling that promotes fibroblast activation, inflammation, and tissue remodeling.
• IGF1R plays a significant role in the abnormal immune response and tissue changes seen in TED.

TSHR (Thyroid Stimulating Hormone Receptor):

• TSHR is a receptor normally found on thyroid cells, where it regulates thyroid hormone production.
• In TED, TSHR is also found on orbital fibroblasts (cells around the eyes).
• This receptor becomes a key target in the disease process because the immune system mistakenly attacks it, leading to inflammation and tissue changes around the eyes.

TSAb (Thyroid Stimulating Antibodies):

• TSAb are autoantibodies produced by the immune system that stimulate the TSHR.
• In Graves’ disease and TED, TSAb bind to TSHR on thyroid cells and orbital fibroblasts, activating them.
• This activation causes overproduction of thyroid hormones and stimulates fibroblasts in the orbit to proliferate and produce substances causing inflammation and swelling.
• The action of TSAb is like an overenthusiastic messenger pushing TSHR to work overtime, which contributes to the eye symptoms in TED.

Neurons: These are the fundamental nerve cells that transmit electrical signals in your brain and spinal cord. In MS, neurons themselves aren't the primary target, but they can be affected indirectly. The damage to the protective myelin sheath around the neurons slows down or blocks these signals, leading to the various neurological symptoms seen in MS.

Myelin Basic Protein (MBP): MBP is a key protein component of the myelin sheath, which insulates nerve fibers and allows rapid signal transmission. In MS, the immune system mistakenly recognizes MBP as a harmful substance and attacks it. This immune attack leads to degradation of the myelin sheath—a process called demyelination—resulting in impaired nerve function.

Beta Cells: These are specialized cells in the pancreas that produce insulin, a hormone crucial for regulating blood sugar levels. In type 1 diabetes, the immune system mistakenly targets and destroys these beta cells, leading to insufficient insulin production.

MHC Class I (MHC I): These molecules are found on the surface of almost all nucleated cells, including beta cells. They present protein fragments (peptides) from inside the cell to the immune system. In type 1 diabetes, beta cells present abnormal or self-peptides via MHC I, which can trigger immune recognition.

APC (Antigen-Presenting Cell): These are special immune cells, like dendritic cells, macrophages, and B cells. Their job is to find harmful invaders (like viruses or bacteria), break them down, and then present small pieces of these invaders, called peptides, on their surface. This process helps alert other immune cells to the threat.

Peptide: A peptide is a small fragment of a protein, often from a pathogen or infected cell. APCs display these peptides on their surface using molecules called MHC, which helps T cells recognize and respond to the invaders.