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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

similarities between prokaryotic cell and eukaryotic cell
Ednah Reply
Eukaryotic cells contain membrane-bound organelles, including a nucleus. ... Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle. Prokaryotes include two groups: bacteria and another group called archaea.
what is different between plasma and serum?
difference between plasma and serum is that plasma is liquid n serum is fluid
what is microbiology
what is the diseases caused by the microorganisms
both cells have plasma membrane, which services as a barrier between the inside of the cell and outside. both prokaryotes and eukaryotes have ribosomes. they receive messages from messanger RNA molecules, telling them what proteins the cell needs.
Some bacteria infection
what is the name given to infection got from the hospital
Nosocomial infection
what is the apportion
what is the main functions of organelles
what is main function of right and left side of the brain.
Salifu. microbiology is the study of oganisms that are too small for the naked eyes to see. this include bacteria
Cabdi. apportion is to divide or share out
what are pathogens
Oluka Reply
any disease causing microorganism that can invade the body and cause harm
hepatitis b
what's da answer
any diseases that course harmful to body
hepatitis is usually implementery of the liver and is commonly course by virus infection
a type of virus that causes severe illness lasting from two to six weeks it may cause massive lived necrosis and cirrhosis
hepatitis B are transmitted when in contact with body fluid such as blood,semen,varginal secration that contain the hepatitis b virus
I understand necrosis,means death of all cell or injury of blood supply, but what is cirrhosis pls
sorry meant liver cirrhosis
good evening all
ok liver damage
I have a question
Hey welcome all of you...i think you are discussing about Micro-organisms..what does it Micro?
how about, scabies (bacteria) yeah can some one gist me abt it
sorry what doest it mean Micro organism?
microorganism are minute living organisms found almost everywhere. they can be autotrophic heterotrophic or chemotrophic
Tell me about enzyme kinetics
wowoww thanks a lot farmuyiwa Alice
have anyone colony pigmentation of different types of bacteria such as Aeromonas, Edwardsiella, vibros,
yes dear sadiqur Bacterias are live in everywhere.. .
microorganisms are arganism that cannot been seen with 👀 until by the use of microscope
microorganisms are arganism that cannot been seen with 👀 until by the use of microscope
yhea organisms are organisms they are naked eye/can't seen by our eyes
and scabies are one of the most common skin condition that can course itches and raches.
and also scabies are not infection, but an infestation
my Q is what is the contribution of van-leeuwenhoek in field of microbiology
Antony van leevenhoek is father of microbiology.
Anton Van leewun hook is discovered Microscope it's true or not? who can brief me please
micro organisms are organism that cannot be seen with an aided eyes ,but by the use of microscope
Yes.. He discover first microscope. He take 2 lence at a time and he saw the plant cells... Thus he was called father of microbiology
who examined water from a bathtub and discovered microbes
for instance any type of Stagnant water is creat there are d/t tupes of small animals.. so those animals are called Micro organism?
thank you javpal for Describing.
can you please differentiate between vacuoles and inclusion bodies
Noor Reply
vacuoles consists of watery solution called cell sap while bodies are organelles
5 difference please
Archaea is an odd type of bacteria that live in extreme environments; high salt, high temperature etc. usually called extremophiles.
Danesia Reply
you know anyone that has delt with enterobacter agglomerans.
it is a type of gram negative bacteria and its ubiquitous mostly isolated from plant stuffs and also from faecal material of animals. I heard the name pantoea . it is bacillus in structure.
What are the classification of microorganisms
Portia Reply
Basic classification are eukaryotic and prokaryotic..
micro organisms are classified into three namely: Archaea, eukaryote and prokaryotic organisms
Yay that's right
what is archaea
I've got an issue with the message view
Frank Reply
Is there any effective way to learn microbiology.
Frank Reply
I have some basic knowledge of biology. I mean i'm totally beginner in that field.
Assuming that i'm interested in neuroscience. What is the best way to master that particular subject.
Can you wait me just a minute
Iam apologies for guidance you in neuroscience.. I'm not physician.. I'm microbiologist
My pleasure to join to you
Let's begin a conversation
Frank Reply
What would be saying
do you know anything about microbiology
I have so much studying to catch up on🙄
any study tips
Yas of course
What would you like to know
well i'm studying Pharmacy second year and i just started With Microbiology
if you have any basics to tell us 🤷🏻‍♀️ would be helpful
Yas, first you must know that you will have a very easy lecture..
In second stage you will try to learn the type of microbiology
A simple definition for microbiology
In second stage you will try to learn the type of microbiology.. you must learn the bacteria..its structure.. Classification of bacteria according to shape..
It's so easy
What triggers the natural killer cells
jenipher Reply
microbiology is the study of science which deals with study of microorganism e.g .virus,bacteria
sufian Reply
microbiology is a branch of science that deals with invisible microorganisms.
microbiology is the branch of science which deals with the study of organisms too small to be seen with the naked eye
what is microbiology
Safwan Reply
history of microbiology
give all details about cell
Samim Reply
Give me another names for all hypersensitivity
Don Reply
Give me the modern father of microbiology
Antonie van Leeuwenhoek
Louis pasteur is father of modern microbiology Antonie van Leeuwenhoek is only the father of microbiology
Antonie van Leeuwenhoek was the first person to observe the mos. whereas pasteur is the one who described about the vaccine , pasteurization etc.
what is the virulence factor
mukhtar Reply
is the abilityof pathogen that cause disease
Practice MCQ 5

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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