CELLS AND ORGANS OF THE IMMUNE SYSTEM miCORBIOL

Basic BSC Microbiology laboratory-template-16x9.pptx

1. CELLS & ORGANS OF THE IMMUNE SYSTEM

2. Role of Immune Cells I t defend the body against the pathogens. NK cells kill virus infected cells and cancer cells. Killing the pathogens using macrophages / process phagocytosis. Antigen presenting cells watch /observe our body like sentries and spies. Antigen presenting cells deposits peptide fragments of pathogen on their surface to recognized other immune cells.

3. Cells at Glance

4. The cells concerned with the defense system of the body are called immune cells Lymphocytes i . B Ly’s ii. T Ly’s iii. Null cells iv. Natural Killer cells (killer cells) Macrophages Dendritic cells Eosinophil Basophils Neutrophils Antigen Presenting cells Mast cells

5. 1. Lymphocytes Lymphocytes are mononuclear and non granular cells of lymphoid tissue participating in immunity They are foundin blood, lymph and lymphoid tissues such as spleen, lymph nodes, tonsils, appendix etc., small large

6. Types of lymphocytes T Cells (T lymphocytes): These cells mature in the thymus gland and are responsible for cell-mediated immunity. They recognize specific antigens presented by infected cells or other antigen-presenting cells. T cells include several types such as: Helper T cells (CD4+): Coordinate immune responses by secreting cytokines. Cytotoxic T cells (CD8+): Kill infected cells directly.

7. Types of lymphocytes contd., B Cells (B lymphocytes ): These cells mature in the bone marrow and are responsible for humoral immunity. They produce antibodies that bind to specific antigens, marking them for destruction by other immune cells.

8. Types of lymphocytes contd., Null cells Lymphocytes null cells" typically refers to a type of lymphocyte that lacks surface markers. These cells were historically considered to be "null" because they did not express. But over time, it was discovered that they actually function the same as B cells

9. Types of lymphocytes contd., Natural Killer (NK) Cells: NK cells are lymphocytes of the innate immune system that play a crucial role in the rejection of tumors and virally infected cells. They are known for their ability to recognize stressed cells without the need for prior antigen exposure.

10. 2. Macrophages Macrophages are a type of immune cell that plays a key role in both innate and adaptive immunity. They are derived from monocytes, which are a type of white blood cell. Here are some important characteristics and functions of macrophages:

11. Macrophages contd Phagocytosis- engulf/ digest- bact , vir , damaged cell debris. Antigen presentation- Hand over the antigen (fragments of the pathogens) using histo - complex molecules. Cytokine production – stimulate immune response- eg . Interleukin-1 (1L-1) which help immediate immune reactions Tissue repair and remodel / Activation and polarization- promote tissue health repair and growth

12. 3 . Dendritic cells Regulates immune response of outer layer tissues contact with external environment. ( eg . Skin, lungs and intestines) Uses: Antigen presentation, Antigen presenting (increasing expression) Regulates cytokine secretions. Linkage Innate and Adaptive immunity Overall, dendritic cells are critical for the initiation of immune responses against infections, tumors, and other challenges. Their ability to capture antigens, process them, and present them to T cells in a context that determines immune activation makes them key regulators of immune responsiveness.

13. 4 . Eosinophil E osinophils are specialized immune cells that play essential roles in defending against parasitic infections and modulating allergic responses. Their functions are tightly regulated and contribute significantly to maintaining immune homeostasis and responding to various challenges in the body . (release toxins to kill parasites| large immune granules – effective | reasons for syndrome )

14. Too many: High levels can indicate allergic conditions, asthma, or certain infections. Too few: Low levels might weaken the immune response against parasites. 4 . Eosinophil cntd

15. 5 . Basophils Basophils are a type of granulocyte, a category of white blood cells that contain granules with various substances important for immune responses. Basophils are involved in immediate hypersensitivity reactions (allergic reactions) by releasing histamine, which triggers symptoms such as itching, swelling, and mucus production . They contribute to the inflammatory response by releasing cytokines and other mediators that attract other immune cells to the site of injury or infection . Basophils are found in the bloodstream but are less numerous compared to other types of white blood cells . Diagnostic Importance: Elevated basophil counts can indicate certain allergic conditions or chronic inflammatory diseases.

16. 6 . Neutrophils Neutrophils are the most abundant type of WBCs. They account for 60-65 percent of total WBCs present in the body. They have an irregular shaped nucleus. They are phagocytic in nature. They engulf pathogens and destroy them . Neutrophils help prevent infections by blocking, disabling, digesting, or warding off invading particles and microorganism. Neutrophils contain granules filled with enzymes and antimicrobial substances that aid in killing pathogens . Elevated neutrophil counts ( neutrophilia ) can indicate bacterial infections, while low counts (neutropenia) can increase susceptibility to infections.

17. 7. Antigen Presenting Cells APCs are specialized immune cells that capture and present antigens to T cells, playing a critical role in the initiation and regulation of Immune responses against infections and other challenges to the body's defenses. B Cells, T Cells and Other immune cells

18. Mast cells are a type of white blood cell involved in the body's immune response, particularly in allergic reactions and defense against parasites . They are primarily located in connective tissues, including the skin, lungs, and gastrointestinal tract, where they play a crucial role in the inflammatory process. 8 . Mast Cells