https://padlet.com/imerare/zaybi0jecvjs en-us 2019-10-01 07:50:01 UTC 2025-12-04 20:53:13 UTC hello@padlet.com imerare https://padlet.com/imerare/zaybi0jecvjs/wish/391723507 T Cell
The mechanism of action of T cell towards the infection.

T cell  and B cell require 3 signals (APC, Co-stimulation, and Cytokine:Amplification) in order to be activated.
APC will present antigen to either T or B cell and in turn it activate the effector cells to express CD40 and CD28. It helps the T cell and B cell to form ligand to APC via CD40L and B7. This act as co-stimulation on the T cell and B cell to release cytokines such as IL-4,5,6,8 to further activation.

Then, it will further differentiate into T helper 1/2, Cytotoxic T cell, plasma and memory cell in adaptive phase.

Th1 is able to kill intracellular pathogen whereas Th 2 is used to kill extracellular pathogen by activation of B Cell into plasma and memory cell.

T regulatory As the name suggests regulatory T cells (also called Tregs) are T cells which have a role in regulating or suppressing other cells in the immune system. Tregs control the immune response to self and foreign particles (antigens) and help prevent autoimmune disease. Tregs produced by a normal thymus are termed ‘natural’. Treg formed by differentiation of naïve T cells outside the thymus.
B cell
There are two types of activation which is the T cell independent activation and the T cell dependent activation.
During the T cell independent activation, B cell binds to similar repetitive epitopes on the antigen and activates the B cell to differentiate to plasma cells. This plasma cell only secrete IgM which plays a role during primary response.
During T cell dependent activation, B cell binds to multiple epitopes of antigen and degrade the antigen to smaller peptides. The smaller peptides are then transported to membrane surface by MHC class II. T helper cell recognises the antigen presented and along with the co-stimulator,binds to it. T helper cell then secrete cytokines that activate the B cells. With the help of T helper cell, B cell differentiates into plasma cell and memory cells. The plasma cells in this stage allows class switching from IgM to IgA,IgG,IgE and IgD which play a role in secondary response. These immunoglobulins can neutralize antigen, allow opsonization and also complement activation.

Macrophage
Macrophage recognize PAMPs on the antigen by using the Pattern recognition receptor (PRR) such as toll like receptor to initiate the phagocytosis activity. In addition, C3a or C5a also attract macrophage to site of infection to engulf the pathogen. Macrophage can also be activated by binding to the Fc receptor of antibodies that from the antigen-antibodies complex. It then leads to phagocytosis activity.

Macrophage can be divided into M1 and M2. M1 is stimulated by interferon gamma that is secreted by NK cell, Th1 T cell, and CD8 T Cell. M 1 is more to induce inflammatory response by secreting pro inflammatory cytokines such as IL-6, IL-12, TNF-a, CXCL8 to cause fever, increased vascular permeability, and recruitment of other effector cells like neutrophils. Whereas M2 is stimulated by IL4, IL-13 which is secreted by mast cell, eosinophils and Th2 T cell. Its function is to resolve inflammation and to repair body tissues. First, it will secrete proteases and stimulate fibroblast to secrete collagenase. These two secretions' function is to cleared off damaged connective tissue and collagen. Whem the removal of damaged cell is done, formation of new tissues begin. M2 will produce VEGF (vascular endothelial growth factor) for angiogenesis and IL-1 which stimulates fibroblast to produce collagen.

Macrophage can kill pathogen in two ways which are the oxygen dependent and independent.

Oxygen dependent is more effective in killing as it produces the hydrogen peroxide and hypochlorite which are more toxic to the pathogen.

Oxygen independent is less effective as it only contains lysozyme, lactoferrins, hydrolytic enzyme, protease and damage membrane of bacterial.

Nitric oxide and reactive oxygen species are generated via the up-regulation of gene from IFN-y to inhibit bacterial, and fungal growth. Besides, it can also minimize the possibility of the macrophage to become the host of intracellular pathogen.

There is also specialized population of macrophages that resides in the tissues. The macrophages are sessile and they help in supporting the physiological function of the tissues. The macrophages will also protect the tissues from inflammatory damage. For example, the macrophages inside the brain are called microglial cells and the macrophages inside the liver are called Kupffer cells.]]> 2019-10-01 07:52:37 UTC https://padlet.com/imerare/zaybi0jecvjs/wish/391723507 imerare https://padlet.com/imerare/zaybi0jecvjs/wish/391723630 T cell
how is T cell activated?
what will T cell do after activation?
Signals required to activate T cell?
What is the response of T cell?

B cell
How plasma cell produce antibodies?
Signals required to activate B cell?

Macrophage
what are the types of macrophage?
what is the difference of oxygen independent and dependent macrophage?
Function of cytokines in activation of macrophage?

]]> 2019-10-01 07:53:01 UTC https://padlet.com/imerare/zaybi0jecvjs/wish/391723630 imerare https://padlet.com/imerare/zaybi0jecvjs/wish/391723808 T cell
CD8, CD4
Types: T helper 1/2, T cytotoxic

B cell: differentiate into plasma and memory cell
Function: to produce antibodies

Macrophage
Function: to engulf pathogen via phagocytosis


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