#Immunology #Thelpercells #CD4+ #Bcells #Lymphocytes #Plasmacells #Immunesystem #Immuneresponse #Tcells #Tcellactivation #Tcelldevelopment

Helper T cells | CD4+ and B cells | Lymphocytes | Immunology

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The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the immune system, particularly in the adaptive immune system. As their name suggests, they "help" the activity of other immune cells by releasing cytokines, small protein mediators that alter the behavior of target cells that express receptors for those cytokines. These cells help to polarize the immune response into the appropriate kind depending on the nature of the immunological insult (virus vs. extracellular bacterium vs. intracellular bacterium vs. helminth vs. fungus vs. protist). They are generally considered essential in B cell antibody class switching, breaking cross-tolerance in dendritic cells, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages and neutrophils.

Mature Th cells express the surface protein CD4 and are referred to as CD4+ T cells. Such CD4+ T cells are generally treated as having a pre-defined role as helper T cells within the immune system. For example, when an antigen-presenting cell displays a peptide antigen on MHC class II proteins, a CD4+ cell will aid those cells through a combination of cell to cell interactions (e.g. CD40 (protein) and CD40L) and through cytokines.

00:00:00
Explaining Immunology concept with the help of an attacking bacteria;
Body's Inflammatory Response; changes in microcirculation;
Role & importance of Neutrophil response; Macrophages.

00:06:05
Immune Response to bacteria in detail; Bacterial mosaic antigenicity; Phagocytosis;
Role of lymphatics in clearing away bacterial antigens ("Free Antigens").

00:11:25
Macrophages; antigen presentation for immune system;
Explanation at the genetic level; mRNA & protein formation; antigen processing/"labelling" of antigen;
Presentation (by macrophages) of antigen to "Immune headquarters"(Lymph Node);
T & B Lymphocytes.

00:22:35
Antigen Presentation continued; Importance of MHC-II molecules in Immune Compatibility;
Expression on surface of macrophages; Antigen Presenting Cell (APC).
T-Cell Receptors (TCR); unique for every single T-cell.

00:32:45
Macrophage; Antigen Processing followed by Antigen Presentation (APC) to T-Lymphocytes;
Functioning of TCR & MHC-II in determining compatibility during the antigen-presentation process, with the T-Lymphocytes;(1st signaling).
CD4; "Clonal Selection".

00:42:40
Following Clonal Selection; Interleukin-1(IL-1) importance in "molecular talking" b/w two leukocytes.
B7 molecule & CD-28 receptor; Role in Co-stimulation (2nd signal)
Immunosuppressant drugs work on this pathway.
T-Cell Selection completion.

00:49:45
T-cell functioning; Mitosis of Selected-T-cell ensues; "Clonal Expansion".
Role of Interleukin-II(IL-2) & IL-2 receptor.
Recap.
Autocrine pathway named. T-Cell proliferation through mitosis; "Expanding of clone".

00:57:10
Recap.
T-cell functioning continued: Clonal Expansion.



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