B and T cells

B and T cells

Humoral responce
1. Is activated when the infection is no in any cell
2. Activation phase
  1. 1. Antigen-presenting cells engulf and breakdown antigens that are invading the host organism via the usage of Lysozyme
  2. 2. Broken down antigens combine with MHC 2 proteins and are presented to the surface of the APC
  3. 3. Helper T cells recognise the MHC-2 and antigen complex and bind to the APC
  4. 4. The binding activates the APC to release cytokines that activate the Helper T cell
  5. 5. The activated helper T cell then releases cytokines that help it proliferate causes more T cells to be made with the specific MHC-2 complex receptor
3. Effector phase
  1. 6. A B-cell with an igm-receptor that corresponds to the antigen attaches to the pathogen
  2. 7. The antigen is then engulfed with the receptor and they are both degraded via lysozyme
  3. 8. The MHC-2 and antigen bind to form the MHC-2 complex and are presented onto the surface of the B-cell
  4. 9. The helper T-cell and B-cell bind causing the helper T-cell to release cytokines that cause the B-cell to proliferate into many identical B-cells
  5. 10. The new B-cells either form plasma cells or memory cells
    1. 10.1. Plasma cells release antibodies that are specific to the antigen present and bind to the antigen via lock and key for killer cells to attach, engulf and breakdown
    2. 10.2. Memory cells remain after the infection is treated incase the antigen attacks again
Cellular Responce
1. Activation Phase
  1. 1. Antigen-presenting cells engulf and breakdown antigens that are invading the host organism via the usage of Lysozyme
  2. 2. Broken down antigens combine with MHC 2 proteins and are presented to the surface of the APC
  3. 3. Whilst this occurs the virus infects epithelial cells, these cells also use lysozyme to breakdown the antigen and present it with MHC 1 to the surface
  4. 4. A helper T cell recognises the MHC-2 and antigen complex on the APC
  5. 5. The helper T cell release singling proteins bringing more and more helper T cells, Cytotoxic T cells (CD8+)
2. Effector Phase
  1. 6. Cytotoxic T cells recognise the MHC1 and antigen complex presented on the endothelial cells and bind to the complex
  2. 7. The binding causes the release of Perforin, which punches holes into the infected cells causing lysis
  3. 8. As the infection comes under control regulatory T cells inactivate the Cytotoxic T cells
  4. 9. Memory T cells remain behind incase the infection begins to attack again
3. Is activated when a cell is already infected
B cells
1. General Facts
  1. 15% of lymphocytes
  2. Matures in bone marrow
  3. Generally need T cells for activation
  4. Effective antigen presenting cells
2. Antigen recognition
  1. MHC 2 is unregulated
  2. Anti CD40 induce B cells response to Ab-Ag + IL-4= mimics T cell
  3. No further signal from IL-4 or BCR = cell death
3. B cell after differentiation into plasma cells helped by T cells, become Antibody factories
T cells
1. General facts
  1. Two types
    1. CD4+ 65%
    2. CD8+ 35%
  2. Originates in bone marrow but matures in the thymus
  3. After negative and positive selection at the thymus they acquire the capacity to distinguish self from non self.
2. Antigen recognition
  1. The combination of TCR binding peptide with either the MHC 1 or MHC 2 allows the T cell to recognise antigens
  2. For recognition TCR must bind with other accessory proteins to make a TCR complex
  3. The signal is not transduced by the TCR but by the accessory proteins, which causes a cascade of events causing cell action
3. T cell receptors recognize peptides only when they are presented by the MHC

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	Created by Ibi Qemlas about 9 years ago