The immune response is the body’s mechanism for safeguarding itself against harmful agents. It consists of multiple defence lines against various microbes and includes specialized, highly specific responses to individual threats. This immune response can be either innate and nonspecific or adaptive, acquired, and highly specific.
Innate Immunity vs. Acquired Immunity
- Innate immunity is the body’s inherent defence system, present from birth, that immediately responds to foreign invaders without prior exposure. It doesn’t require training to distinguish self from non-self and lacks memory of past encounters.
- Acquired immunity, also known as adaptive or specific immunity, develops over time through exposure to pathogens. Specialized white blood cells, lymphocytes, retain the memory of specific invaders, enabling a swift and targeted response upon subsequent exposures. Vaccines enhance acquired immunity by priming these cells to recognize and combat potential threats before they cause illness.
Cells of the innate immunity are:
- Phagocytes (monocytes, macrophages, neutrophils, and dendritic cells)
- Natural killer (NK) cells
Cells of the adaptive response are:
- T Lymphocytes classified as CD4+T cells and CD8+T cells
- B Lymphocytes differentiate into plasma cells, which produce specific antibodies
The immune system is a sophisticated network composed of organs, cells, and proteins that safeguards the body from infections while preserving its own cells. It keeps a memory of every microbe it has previously defeated, allowing it to swiftly recognize and eliminate the microbe if it re-enters the body.
Part of the Immune System
- White blood cells: White blood cells are pivotal components of the immune system. These cells are produced in the bone marrow and are integral to the lymphatic system. They circulate through the bloodstream and tissues, constantly surveilling for pathogenic invaders such as bacteria, viruses, parasites, and fungi. Upon detecting these foreign entities, white blood cells initiate an immune response. This category of cells encompasses lymphocytes, including B-cells, T-cells, and natural killer cells, as well as various other types of immune cells.
- Antibodies: Antibodies are crucial components of the immune system, playing a vital role in defending the body against pathogenic microbes and the toxins they produce. These immunoglobulins achieve this by specifically identifying and binding to unique molecular structures known as antigens, which are present on the surface of the pathogens or within their secreted toxins. This antigen-antibody interaction marks the pathogen or toxin for subsequent elimination. The immune response involves a complex interplay of various cells, proteins, and biochemical mediators to effectively neutralize and eradicate the foreign entities.
- Complement System: The complement system is a sophisticated network of plasma proteins that enhances the efficacy of antibodies in immune defence. This system operates synergistically with antibodies, facilitating the opsonization and lysis of pathogens, thereby complementing the humoral immune response.
- Lymph Nodes Lymph nodes are small, bean-shaped structures that function as filtration units within the lymphatic system, akin to colanders used for draining pasta. These nodes are essential for filtering waste products from the lymphatic fluid, which drains from tissues and cells, while retaining beneficial components such as nutrients. Distributed extensively throughout the body, lymph nodes play a critical role in maintaining immune surveillance and facilitating the removal of cellular debris and pathogens from the lymphatic circulation.
- Spleen: The spleen serves as a reservoir for white blood cells crucial for immune defence against foreign invaders. Additionally, it functions as a blood filter, responsible for recycling aged and impaired red blood cells to facilitate the production of new ones.
- Thymus: The thymus gland, a small organ located near the heart, plays a pivotal role in the maturation of T-cells, a specialized subset of white blood cells. These mature T-cells then migrate to various parts of the body to orchestrate immune responses and protect against infections.
- Bone Marrow: Bone marrow, a soft and fatty tissue found within bones, acts as a hematopoietic factory essential for the production of blood cells critical for physiological functions. This includes the generation of white blood cells, which play integral roles in immune surveillance and defence mechanisms within the body.
In addition to the immune system, the body employs several other mechanisms to defend against microbial threats:
- Skin: Acting as a waterproof barrier, the skin secretes oils with bactericidal properties, providing a first line of defence against pathogens.
- Lungs: Mucous in the lungs, known as phlegm, serves to trap foreign particles, while small hair-like structures called cilia move the mucous upward for expulsion through coughing, aiding in the removal of potential pathogens.
- Digestive Tract: The mucous lining of the digestive tract contains antibodies that contribute to immune defence. Furthermore, the acidic environment in the stomach is hostile to most microbes, effectively neutralizing them.
Immunoglobulin Therapy
Immunoglobulin therapy, also known as immunoglobulin replacement therapy (IRT), is used to treat individuals who cannot produce sufficient antibodies or whose antibodies are ineffective. Traditionally, this involved intravenous immunoglobulin (IVIg) therapy, where antibodies are delivered via a drip into the vein. Recently, subcutaneous immunoglobulin (SCIg) therapy, which injects antibodies into the fatty tissue under the skin, has become an alternative, potentially benefiting some patients. Both therapies use plasma-derived antibodies.
For more details, refer to the Subcutaneous Immunoglobulin information sheet. If interested, discuss SCIg therapy with your clinical immunology/allergy specialist.
Immunization
Immunization mimics the body’s natural immune response by introducing vaccines, which contain small amounts of treated viruses, bacteria, or toxins. This prompts the body to produce antibodies, ensuring immunity if exposed to the actual pathogen.
Vaccinations protect against diseases like measles and tetanus. Immunization needs are based on health, age, lifestyle, and occupation, collectively referred to as HALO:
- Health: Conditions such as asthma, diabetes, heart, lung, spleen, or kidney issues, Down syndrome, and HIV may require additional or frequent vaccinations.
- Age: Different age groups need protection from various diseases, as outlined by Australia’s National Immunisation Program. Recommended vaccines are often free for at-risk groups.
- Lifestyle: Factors such as travel, family planning, sexual activity, smoking, and contact sports can influence immunisation needs.
- Occupation: Jobs that expose individuals to diseases or vulnerable populations may require extra or more frequent vaccinations. Discuss with your doctor if you work in aged care, childcare, healthcare, emergency services, or sewerage maintenance. Some employers may cover vaccination costs.