Introduction: Basic concepts Flashcards
Inappropriate response:
Sepsis - overreaction
Allergy and asthma – oversensitive
Chronic inflammatory disorders – no resolution
Autoimmune diseases:
diabetes type I, multiple sclerosis,
rheumatoid arthritis, systemic lupus erythematousus
Immunodeficiencies:
Primary (genetic) (Severe Combined Immunodeficiency)
Secondary/acquired (AIDS, resulting from HIV infection)
Innate immune system:
Adaptive immune system:
Primary lymphoid organs:
generation of leukocytes (bone- marrow), and maturation of lymphocytes – B-cells in the marrow, T-cells in the thymus.
When mature, they leave the primary organs and circulate in the blood and the lymphatic system.
Secondary lymphoid organs:
where mature (but naïve) lymphocytes meet antigens and the adaptive immune response develops
Primary organs:
- Bone marrow
- Thymus gland
Secondary organs:
- Spleen (filter blood)
- Lymph nodes (filter lymph)
- MALT = mucosa associated tissue: Peyer`s patches, tonsils, appendix
hematopoietic stem cells
Within the bone marrow, HSCs are constantly renewed and directed to differentiate into two major types of progenitor cells
Important first line defence:
Express granules containing proteases, antimicrobial proteins++
Neutrophils
phagocytic and bactericidal, first at the site of infection but short-lived
Basophils/mast cells
inflammation/allergies
Eosinophils
kill antibody coated parasites
Myeloid cells I:
Granulocytes
Myeloid cells II:
Monocytes and Macrophages
Blood Monocytes
migrate into the tissues (cytokine exposure) and differentiate into Macrophages
Arrive later at site of infection than neutrophils and live longer
Dendritic cells
Heterogenous: arise both from myeloid and lymphoid (monocytes can differentiate to DCs)
Phagocytic, professional antigen-presenting cells
In tissues, the DCs monitor the environment for signs of invasion by pathogens the skin (Langerhans cells) and the mucosal lining (nose, lungs, stomach, intestines)
Upon infection: Capture and process antigens, migrate to lymph nodes to present antigens to T-cells.
Links innate and adaptive immunity
T cells (adaptive)
- Developing in the thymus: clonal selection
- Express rearranged T-cell receptor (TCR)
T-cell Effector cells:
T helper cells (CD4+, different sub-
types), T cytotoxic cells (CD8+), memory cells
B cells (adaptive)
- Express rearranged B cell receptors (BCR)
- Antigen-presenting cells
B cells effector cells:
plasma cells that release antibodies,
memory cells
Secondary lymphoid organs: effector responses
Areas where lymphocytes encounter antigens, become activated, undergo clonal expansion, and differentiate into effector cells and memory cells
Innate immune cells: pattern recognition
Innate immune cells have germ-line encoded pattern-recognition receptors that recognise conserved microbial patterns and damaged/erroneous self
