What is Cells: Definition and 450 Discussions

A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be easily distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface.
T cells are born from hematopoietic stem cells, found in the bone marrow. Then, developing T cells migrate to the thymus gland to mature. T cells derive their name from this organ where they develop (or mature). After migration to the thymus, the precursor cells mature into several distinct types of T cells. T cell differentiation also continues after they have left the thymus. Groups of specific, differentiated T cell subtypes have a variety of important functions in controlling and shaping the immune response.
One of these functions is immune-mediated cell death, and it is carried out by two major subtypes: CD8+ "killer" and CD4+ "helper" T cells. (These are named for the presence of the cell surface proteins CD8 or CD4.) CD8+ T cells, also known as "killer T cells", are cytotoxic – this means that they are able to directly kill virus-infected cells, as well as cancer cells. CD8+ T cells are also able to use small signaling proteins, known as cytokines, to recruit other types of cells when mounting an immune response. A different population of T cells, the CD4+ T cells, function as "helper cells". Unlike CD8+ killer T cells, these CD4+ helper T cells function by indirectly killing cells identified as foreign: they determine if and how other parts of the immune system respond to a specific, perceived threat. Helper T cells also use cytokine signaling to influence regulatory B cells directly, and other cell populations indirectly.
Regulatory T cells are yet another distinct population of T cells that provide the critical mechanism of tolerance, whereby immune cells are able to distinguish invading cells from "self". This prevents immune cells from inappropriately reacting against ones' own cells, known as an "autoimmune" response. For this reason, these regulatory T cells have also been called "suppressor" T cells. These same regulatory T cells can also be co-opted by cancer cells to prevent the recognition of, and an immune response against, tumor cells.

View More On Wikipedia.org
Recent contents Top users
  1. P

    Exploring Gamma Waves and Their Impact on Human Cells

    hi my friends I want some informations to study about gamma wave and interactions of it on humans cells.thancks alot.
  2. S

    Daniell Cells - Effect of conditions

    Homework Statement I am doing a chemistry extended experimental investigation on the variables affecting a Daniell Cell's voltage. I am required to understand the reasoning behind voltage increase and decrease for particular conditions. I have done extensive research, but am unable to find a...
  3. B

    Mechanism by which cells adhere to each other

    What is the mechanism by which they adhere to each other, and what stops them from sticking together when say you put your hands together?
  4. P

    Understanding Voltaic Cells: The Role of Fe3+ in the Anode

    The problem I have is just a detail I want to clarify about the voltaic cell. A standard cell is a voltaic cell in which each half-cell contains all entities shown in the half-reaction equation at SATP conditions, with a concentration of 1.0 mol/L for the aqueous solution. Referring...
  5. S

    What Are Cells in a Laptop Battery?

    Hi, Im looking for a new laptop battery. Something that's confusing me is the number of cells in a battery; what is a cell? is it a smaller battery that exists in the larger battery? If so, are the cells connected in series whose voltage sums to the voltage of the total battery? Or...
  6. R

    Using PV cells to energize an air core coil

    I'm using PV cells to energize an air core coil. Is there a method in which I can determine the maximum length of 32 gauge magnetic wire to use, so that I don't use too few windings and burn the coil out or too many windings limiting its' potential. I'll be using 2 PV cells that are each rated...
  7. A

    Question about Cells and Cell Channels

    Imagine that it is possible to design cells of varying size. A cell is to be designed with a membrane that has a stable number of open channels. To this end, the number of channels must meet the following condition: the standard deviation of the number of open channels shall be no more than...
  8. M

    Medical Stem Cells: Blood Transfusions & Biscuits

    Bad news for those of us who like the free biscuits and the little badges but potentially good news for anyone needing a transfusion. http://www.livescience.com/health/090323-embryo-blood.html
  9. O

    Fuel cells versus Batteries

    batteries or fuel cells? hydrogen costs too much to be an effective fuel alternative? the catalyst required for the electrochemical conversion reaction is pricey platinum? Using hydrocarbons as a source for hydrogen we have more CO2 in the atmosphere? and require a high temperature...
  10. G

    Does Simulating 3-D Structures Enhance Polymer Solar Cell Efficiency?

    Is it useful simulating a 3-D structure of a polymer solar cell? Is there a particular internal structure for a polymer solar cell which is most efficient?
  11. T

    Applied ME: Drag Force Calculation with Load Cells & LabVIEW

    Hello, First time post long time lurker! I've got an interesting project I am working on which involves a few MechE subjects. The overall goal (for now) is to determine the drag force of a cylindrical cone headed object in sand under various pressures. The movement of the cylinder is the tricky...
  12. S

    What is the optimal light intensity for studying epithelial cells in microscopy?

    What is the approximate size of epithelia cells from the human oral cavity? And why must light intensity be low when studying them in bright field microscopy? (I know that phase contrast is better).
  13. C

    Medical Are the blood cells just suspended in the liquid we call blood?

    Is blood completely made up of blood cells, like we are completely made of atoms, or are the blood cells just suspended in the liquid we call blood?
  14. belliott4488

    Basic probability question: 1 or more objects in N cells

    Sorry that subject is vague. Here's the question: If I have N objects randomly placed into M cells (M>N), what is the probability that I will find one or more objects in anyone cell? Here's why I'm asking, or rather, here's why I'm confused: I have one object that has been placed at...
  15. T

    Medical 8 letter word for a efficient grouping of cardiac muscle cells

    Doing a homework crossword and this is the last problem. I can't seem to find it anywhere. An efficient grouping of cardiac muscle cells, eight letters long ending in M. Any help would be much appreciated.
  16. H

    Doppler effect measure speed in blood cells

    Homework Statement A Doppler blood flow unit emits ultrasound at 5.0 {\rm MHz}. What is the frequency shift of the ultrasound reflected from blood moving in an artery at a speed of 0.20 m/s? What equations would I use to calculate the doppler shift? It is not in my textbook...
  17. N

    Epodea plant cells the chloroplasts 'retreated'

    Hello! I performed a quick practical today using light microscopes. When looking at Epodea plant cells the chloroplasts 'retreated' to the edge of the cell; the vacuoles weren't particularly large and so didn't appear to be 'pushing' the chloroplasts an awful lot. Also, the chloroplasts at the...
  18. J

    StemEnhance: Is it a Scam or Legit Stem Cell Booster?

    http://img.exigo.com/public/1595/websites/2/images/stemenhance-label-english.pdf Sounds good and all, but I noticed that it is blue green algae. Sounds like a major scam.
  19. N

    Find Best Cell for an Egg, Movement: Help Quick

    Homework Statement Can someone please help A.S.A.P. I have a science assignment due tomorrow and it's 11:00 and I'm getting very frustrated. I'm about to go to bed and i'll forget about it in the morning. Ok i have 3 pictures. i tried drawing them on paint but it won't work, any ideas on how...
  20. T

    Charging a car battery with dry cells?

    If eight flashlight batteries in series have an emf of about 12 V, similar to that of a car battery, could they be used to start a car with a dead battery? Why or why not? My friend posed to me this question and then I just sort of stumbled and was dumbfounded. I answered it by saying the...
  21. V

    I-V Characteristics of Photovoltaic cells

    Hi, could someone care to explain two things: 1) Whats happens when the resistance load of a circuit powered by a PV cell generates a higher voltage then that produced by the PV cell (does band gap get affected). 2) Why does current drop near the Open Circuit Voltage? Surely the generation...
  22. M

    Effects of X-rays on cells and chromosomes

    Could someone PLEASE explain in simple language "procedures whereby scientists modify the germ plasm of plants and animals by the use of X rays?" And, how might that effect chromosomes? If you do not know, please advise where I can find this information. I am not a student and this is related...
  23. Topher925

    Why are heat pipes not used in PEM fuel cells?

    Just curious as to why you don't find heat pipes or any passive cooling in larger PEM type fuel cells. I have seen them used in methanol fuel cells but not FCs for hydrogen. Is there a good reason for this? Is it because the power density of fuel cells is typically higher than that in many...
  24. H

    What is the difference between dendritic cells and FOLLULAR dendritic cells?

    What is the difference between dendritic cells and FOLLULAR dendritic cells? where are these found in the periheral tissues? thanks
  25. B

    Connections Between Skeletal Muscle Cells & AP Transmission

    I know that smooth and cardiac muscle cells (myofibers) are connected to each other by gap junctions. How are skeletal muscle cells connected to each other (to transmit the AP)? Thanks, any responses appreciated
  26. Topher925

    PEM fuel cells, why the membrane?

    For those of you that arent very familiar with PEM fuel cells, their shortcomings basically revolve around the carbon/platinum membrane and is essentially the "heart" of the fuel cell. But why does a fuel cell need a membrane to function? If you think about it, just about all energy conversion...
  27. B

    Memory B and T Cells: How Many and How Long?

    I've learned about memory B and T cells. I'm wondering how many of each a person has for a specific antigen? How long do they live?
  28. F

    How many molecules have a white blood cells

    How many molecules have a white blood cells and red blood cells? What are the chemical description and information about these above molecules?
  29. Phrak

    Calculating the Energy Cost of Manufacturing Solar Cells: Factors to Consider

    How much electrical energy does it take to manufacture a solar cell? I'm curious about the break-even time. Silicon boules are grown in an over--probably electric. More machining follows. If the frame is aluminum, it's smelted in an electric arc furnace. This is really an oversimplifed...
  30. B

    Gene Insertion: Transcription in Eukaryotic Cells

    If one gene is inserted into the sequence of a second gene, will both genes by transcribed in the eukaryotic cell?
  31. P

    Golgi Bodies: Muscle v Cheek Cells Why?

    Why do muscle cells have more golgi bodies than, say, cheek cells?
  32. D

    Programs Masters/PhD - Research in Organic Electronics / Solar Cells

    Hi, I was looking around at graduate schools and was curious if anyone knew of places where they are doing research into organic electronics or organic photovoltaics? I found a research department at MIT and Stanford, but I was looking for something perhaps one tier below that. It...
  33. R

    Potential and electron distribution in circuits and cells

    could anyone shed some light on the following... the language might not be too precise here, but I'm trying to get a feel for the subject in a battery one terminal (metal) has an excess on electrons which have come from the other +ve terminal (metal), this causes a difference in potential...
  34. A

    The Power of Photon Theory: How UV & IR Light Affect Skin Cells

    Ultraviolet light can kill skin cells but infrared light only warms skin cells even though both types of lights are from the sun. Why is this, explain using the photon theory...?
  35. R

    Unit cells (crystal structure)

    I'm trying to clarify for myself the difference between a Unit Cell, a Primitive Unit Cell and a Conventional Unit Cell. As far as I know, Primitive Unit Cells contain only one lattice point and are the smallest possible unit cell Unit Cells are the crystal's smallest building block, and...
  36. R

    Comparing Solar Cells & Panels: Designing Lab Experiments

    last part! hi QUESTION There are two standard methods for the solar energy to be trapped and used domestically. One is to use solar cells, which convert the radiation energy to electrical energy. The other is to use a solar panel, which absorbs the solar radiation to heat water. You...
  37. S

    What are the Anucleate Cells in the Human Body?

    Hi, Can someone provide a list of anucleate cells in human body? i know platelets and red blood cells are anucleate. Are there more? Thanks a million.
  38. B

    Germ Line Cells & DNA Damage: Causes of Aging?

    Do germ line cells accumulate DNA Damage like the rest of the body? I've heard things about them that make them seem to have very different characteristics to the rest of the body. Ie could germ line cells, or anything, contain your original DNA when you're like 50 or 100, or would the only DNA...
  39. X

    Rate of Glucose uptake by yeast cells

    You are required to plan an investigation to find out the rate of glucose uptake by yeast cells varies with glucose concentration material resources - 10% glucose solution - disilled water -yeast suspension - Benedicts reagent I have done the introduction, apparatus required, but I am...
  40. E

    Operating temperature of Fuel Cells

    What does the operating temperature of a fuel cell mean? Is this the temperature the cell generates or the temperature the cell is brought to so that it can operate? I see articles that state operating temperatures for different fuel cell systems---i.e. solid oxide 600 to 1000 C, phosphoric acid...
  41. D

    Yeast cells vs. corn seedling

    1) Will yeast cells or corn seedling have a higher metabolic rate when compared on a mass specific basis? 2) How will decreasing the amount of glucose affect the rate of ATP production by the cells if the amount of yeast is held constant? Answer: the rate of ATP production will...
  42. A

    How did the first cells come about?

    I understand how we get microspheres and coacervates, which aren't really living, but how do we get prom these to the first prokaryotes? I understand that once you have the prokaryotes they can coexist to form eukaryotes and so forth, but I can't seem to find out what that little step is that's...
  43. S

    Difference Between Multinucleate Cells & Plasmodium

    Is Plasmodium an example of a syncytium, or is there a slight difference between the two terms? Thank you.
  44. B

    The Impact of Delta Protein Expression on Aging Cells

    Can you force older cells to express more delta protein? Would the cells expressing more delta protein be good or bad?
  45. L

    Solving Series-Connected Cells & AWG 18 Wire Circuit

    [b]1. Homework Statement [ Six cells are connected in series to form a battery. Each cell has a rating of 1.5 volts and 1 amp. AWG 18-gauge wire joins the positive terminal of the battery formed by the series of cells to an indicator lamp 300ft away. Another 300ft length of AWG 18 wire runs...
  46. P

    Cells and the criteria of life

    Do all cells and microorganisms fulfill the criteria of life? Homeostasis Organisation Metabolism Growth Adaption Response to Stimuli Reproduction I'm asking, because I know that there are animal species which don't fulfill all those criteria (I know a mule can't reproduce) and I was...
  47. B

    Stem Cell Technology in Humans: What's Being Used Now?

    What kind of stem cell technology is being used in humans right now and by what places? I mean some stem cell technology is being used currently in humans right?
  48. H

    Alkaline and Ag O button cells

    I read in maplin.co.uk that SR-41 button cells are superior to LR-41s. In what ways and by how much? Thanks
  49. T

    Miller Indices & Packing Density for HCP Unit Cells

    i have a question. please tell me the Miller Indices for Crystal Planes of HCP unit cells +packing density of it. thank you
  50. T

    Optimizing Salt Bridge Conductivity in Voltaic Cells

    Iam doing an experiment on voltaic cells in particular Iam studying the effect that the thickness of the salt bridge has on the emf of the cell over time. iam thinking that the thicker the salt bridge the longer it will last. I think that will happen because maybe there is more surface area...
Back
Top