Types of Immune Responses
The immune response is broadly divided into two interconnected systems:
1. Innate Immunity (Nonspecific)
This is your body's first line of defense, offering immediate but general protection against all invaders.
- Components include physical barriers like skin and mucous membranes, and cellular components like phagocytes (e.g., macrophages, neutrophils) that non-specifically engulf and destroy pathogens.
- It is not antigen-specific and has no memory.
2. Adaptive Immunity (Specific)
This is a more sophisticated and slower response that targets specific antigens and develops memory.
- Antigen-Specific: It targets unique parts of a specific pathogen (antigens).
- Memory: After the first encounter (the primary response), specialized cells (memory cells) are created, leading to a faster and stronger secondary response upon re-exposure.
The adaptive response has two main branches:
- Humoral Immunity: Mediated by B lymphocytes (B cells) which mature into plasma cells and produce antibodies. Antibodies circulate in body fluids (humor) and neutralize pathogens.
- Cell-Mediated Immunity: Mediated by T lymphocytes (T cells). Cytotoxic T cells directly kill infected or compromised body cells, while Helper T cells coordinate the overall immune response.
Components of the Immune System
The immune system is a network of organs, cells, and proteins:
Organs and Tissues:
- Bone Marrow: Produces all blood cells, including immune cells.
- Thymus: Where T cells mature.
- Lymphatic System: Includes lymph vessels and lymph nodes that filter lymph fluid and trap microbes.
- Spleen: Filters blood, removing microbes and old red blood cells.
Immune Cells (Leukocytes/White Blood Cells):
- Phagocytes (e.g., Macrophages, Neutrophils): Engulf and digest invaders.
- Lymphocytes (B cells, T cells, Natural Killer (NK) cells): Key players in adaptive immunity and directly destroying infected cells.
Proteins:
- Antibodies: Bind to specific antigens to neutralize them or mark them for destruction.
- Cytokines: Chemical messengers that help regulate the immune response.