<< Chapter < Page Chapter >> Page >

Activated helper T cells can differentiate into one of four distinct subtypes, summarized in [link] . The differentiation process is directed by APC-secreted cytokines . Depending on which APC-secreted cytokines interact with an activated helper T cell, the cell may differentiate into a T helper 1 (T H 1) cell, a T helper 2 (T H 2) cell, or a memory helper T cell. The two types of helper T cells are relatively short-lived effector cells , meaning that they perform various functions of the immediate immune response. In contrast, memory helper T cells are relatively long lived; they are programmed to “remember” a specific antigen or epitope in order to mount a rapid, strong, secondary response to subsequent exposures.

T H 1 cells secrete their own cytokines that are involved in stimulating and orchestrating other cells involved in adaptive and innate immunity. For example, they stimulate cytotoxic T cells, enhancing their killing of infected cells and promoting differentiation into memory cytotoxic T cells . T H 1 cells also stimulate macrophages and neutrophils to become more effective in their killing of intracellular bacteria. They can also stimulate NK cells to become more effective at killing target cells.

T H 2 cells play an important role in orchestrating the humoral immune response through their secretion of cytokines that activate B cells and direct B cell differentiation and antibody production . Various cytokines produced by T H 2 cells orchestrate antibody class switching , which allows B cells to switch between the production of IgM, IgG, IgA, and IgE as needed to carry out specific antibody functions and to provide pathogen-specific humoral immune responses.

A third subtype of helper T cells called T H 17 cells was discovered through observations that immunity to some infections is not associated with T H 1 or T H 2 cells. T H 17 cells and the cytokines they produce appear to be specifically responsible for the body’s defense against chronic mucocutaneous infections. Patients who lack sufficient T H 17 cells in the mucosa (e.g., HIV patients) may be more susceptible to bacteremia and gastrointestinal infections. Blaschitz C., Raffatellu M. “Th17 cytokines and the gut mucosal barrier.” J Clin Immunol. 2010 Mar; 30(2):196-203. doi: 10.1007/s10875-010-9368-7.

Subtypes of Helper T Cells
Subtype Functions
T H 1 cells Stimulate cytotoxic T cells and produce memory cytotoxic T cells
Stimulate macrophages and neutrophils (PMNs) for more effective intracellular killing of pathogens
Stimulate NK cells to kill more effectively
T H 2 cells Stimulate B cell activation and differentiation into plasma cells and memory B cells
Direct antibody class switching in B cells
T H 17 cells Stimulate immunity to specific infections such as chronic mucocutaneous infections
Memory helper T cells “Remember” a specific pathogen and mount a strong, rapid secondary response upon re-exposure

Activation and differentiation of cytotoxic t cells

Cytotoxic T cells (also referred to as cytotoxic T lymphocytes , or CTLs) are activated by APCs in a three-step process similar to that of helper T cells. The key difference is that the activation of cytotoxic T cells involves recognition of an antigen presented with MHC I (as opposed to MHC II) and interaction of CD8 (as opposed to CD4) with the receptor complex. After the successful co-recognition of foreign epitope and self-antigen, the production of cytokines by the APC and the cytotoxic T cell activate clonal proliferation and differentiation. Activated cytotoxic T cells can differentiate into effector cytotoxic T cells that target pathogens for destruction or memory cells that are ready to respond to subsequent exposures.

Questions & Answers

sahi kon hai bhosri ke
saurabh Reply
define metabolism of carbohydrates with example
Thavasi Reply
what is sterilization a
Sani
the process of keep equipment free from bacteria
shar
is it only bacteria?
Lois
no undesirable fungi and contamination also.
Khushbu
what is streak plate method
Offikwu
what is the biofilm
Dimingu
metabolism is the sum of all the biochemical reaction required for energy generation and use of that energy to synthesize cell materials from small molecules in environment.
Alex
boclenia
Pooja
what are granulocytes
Shawnitta Reply
e.coli
Sukhdeep
granulocytes are type of WBCs which contains granules in the cytoplasm
Owili
suitable example for prokaryotes
Suvetha Reply
one of the possible early sources of energy was
Suvetha
uv radiation and lighting
Anisha
e coli is the example of prokaryotes
Sukhdeep
archaea too
Noel
which is the specific virus causing typhoid
Jeremiah Reply
it's caused by a virulent bacteria called Salmonella Typhi
Sarah
write the life cycle of HIV
Firomsa Reply
describe the internal and external structure of prokaryotic cell in terms of there appearance and functions
Lenia Reply
compare and contrast similar structures found in prokaryotic and eukaryotic cells
Lenia
control of microorganisms
ISTEFAZUL Reply
what is sterilization
Sani
how can a doctor treat a person affected by endospore forming bacteria in his/her wound?
Mambo Reply
define disinfectant
Sani
the process of killing
shar
the process of killing microorganisms
shar
a 28 years old woman come to your clinic with complain of fever painful genital blisters which express clear fluid when ruptured burning sensation around the bristers what is the diagnosis?
Ramadhani Reply
genital herpes caused by a virus called herpe simplex virus
Doris
what is the reference between selective medium and differential medium?
Tony Reply
the micro flora of air is transient why
Princess
Hello.... Am new here
essien Reply
welcome essien
Muhammad
welcome essien
Beka
I'm new here
kumeiwoe
Welcome Macpue!😊
prosper
classification of gram positive
lissa Reply
classify gram positive
lissa
catalase test is done to differentiate between staph and strep. as staph is catalase positive while strep is catalase negative then staph is differentiate further on coagulase positive and coagulase negative. staph aureus is coagulase positive while staph epidermidis is coagulase negative.
Muhammad
gram positive staph is further differentiated on sensitivity test and manitol salt fermentation test while gram positive strep is differentiated on hemolysis pattern
Muhammad
more about gramm positive
lissa
please
lissa
ok
Blessing
am back any gist
Blessing
taxonomy
Rahul
can i use the graph of bacterial growth for my master's thesis?
Christoph Reply
facultative anaerobic bavteria gives uniform turdibity in nutrient broth why?
Princess Reply
oils and waxes are not sterilized in autoclave
Princess
what is the function of paraffin
Muhammad
@ MAHI because they can grow all over the media from surface to the bottom as they can utilize oxygen or conduct fermentation in its absence.
Online
2.@MAHI Autoclave uses steam under pressure. The steam cannot penetrate through oil and wax. Thus, dry heat sterilization is preferred than autoclave .
Online
thnku
Nadiya
how nutirent agar can converted into blood agar
Princess
thank you
Princess
take a nutrient agar ........and add 5ml blood and put in it ...........!
Nadiya
nutrient agar +blood 5ml+ distilled water =blood agar .
Nadiya
mixed wellllll
Nadiya
hi
Rahul
why agar is not a neutrient source?
Shimul
because it's a general purpose agar only use for growing bacteria
Richa
way is antigen
opaleye
what is antigen
opaleye
antigen is a foreign body that cause activation of antibody?
ASNAKE
Antigen is a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
Shimul
thanks for that
opaleye
what is pharmacology
Luyenu
a science that studies about the drug
ASNAKE
hello ever one
Sayid
y
Abdul
Work hard
Anigor
y
Abdul
thanks alot
Luyenu
What is the major different between gram positive and gram negative bacteria.
Asikur
bacteria kya hai
Mala
content of their cell wall
Doris
koi mujhse basic microbiology ki study k Lea book suggest kro .
Richa
Harley prescott
Vikas
Practice MCQ 5

Get the best Microbiology course in your pocket!





Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask