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

    Virtual cells of mirror reflections

    Homework Statement Please note that this is an extension of this question here: https://www.physicsforums.com/showthread.php?p=4571995#post4571995**Questions** Mirrors A and B with the space between them, including the bird, are part of the real world. Those are all a part of a basic cell...
  2. H

    What Is the Newest Generation of Solar Cells?

    Dose anyone know that what is the newest generation of solar cells?
  3. B

    What is the current in a circuit with two cells?

    Homework Statement What is the current in this circuit: http://img802.imageshack.us/img802/4646/8ekh.png Homework Equations All potential differences in a closed portion of a circuit must add to 0. Terminal Voltage = EMF - I x internal resistance. The Attempt at a Solution I do not know how...
  4. O

    Biology How did they measure total cells? (genetics of bacteria)

    1. About how many cells were plated to count His+ revertant colonies? How was total cell number determined? I know that the mutation freq was out of 10^7 survivors. So they had to measure the total cell number and come up with 10^7 survivors? But I'm not sure how they got this...
  5. O

    Proton Concentration Cell: Finding Original pH with Initial EMF

    Proton concentration cell is made by connecting with Pt wire two acid-base solutions and measuring emf. but wire allows redox reaction, changing conc of H+ in each solution. how is original pH found- with initial emf reading?
  6. O

    Deduce Half-Cell Reactions from Galvanic Cell Representation

    Please tell me how to deduce reliably from galvanic cell representation, the half-cell reactions, for any cell, or vice versa. Pt(s) | H2(g) | HCl(aq) | Cl2(g) | Pt(s) Pb(s) | PbCl2(s) | HCl(aq) | H2(g) | Pt(s) Pb(s) | PbSO4(s) | K2SO4(aq) || KNO3(aq) || KCl(aq) | PbCl2(s) | Pb(s)...
  7. N

    Why Do Cells Die? | AP Biology

    I'm a high school student in AP Biology, and we are learning about how cells can absorb nutrients they need through the plasma membrane, as well as break down glucose into ATP for use. So why do cells (and organisms, for that matter) all of the sudden... Die? Why can't the cell just keep...
  8. M

    Could solar PV cells be made out of aluminum?

    I don't know if this is the right forum but I'm curious. Companies are searching for alternatives like copper and zinc to make photovoltaic solar cells out of. Could aluminum ever work and be feasible, and replace current rare Earth components?
  9. J

    What causes electrons to move from the anode to the cathode in a galvanic cell?

    In a galvanic cell, electrons are supplied by oxidation at the anode. I am struggling to find clarity on what makes the electrons move from the anode to the cathode when a wire is connected between the two. I have come across some texts on the internet that say the electrons are attracted to the...
  10. E

    Band structures with non-primitive cells

    How does one interpret band structures (i.e. E,k solution pairs for a given Hamiltonian) for a non-primitive cell? I was looking at these slides: http://www.tcm.phy.cam.ac.uk/castep/CASTEP_talks_06/clark2.pdf Slide 9 has the "normal" silicon band structure obtained with a primitive cell...
  11. S

    Electrical components connected between cells

    Hi all, I would appreciate a little guidance on some circuit theory. I was wondering how a circuit behaves when there are, say two identical 10V cells, and a 1Ω bulb happily sitting in series, but then one connects another identical bulb between the two cells. Obviously the current in the first...
  12. B

    Are superconducting galvanic cells possible?

    My (chemistry) textbook states that maximum work is never achieved in a galvanic (electrochemical) cell due to frictional heating. I've been wondering, could a cell be made with superconducting wires, cathodes, and anodes in order to achieve maximum work? Would this violate the law of entropy?
  13. R

    PROJECT: Determining weight with load cells.

    First, I am not an electrical engineer and am not to familiar with circuit boards. PROJECT: I have a static load, represented by a block. The block has three very short legs (or feet 3/8" diameter each). The feet are located concentricly under the block. Under the feet I place three thin-film...
  14. L

    The size cells can grow to is limited. Of the cells shown, which one

    "The size cells can grow to is limited. Of the cells shown, which one" Practice test question: 12) The size cells can grow to is limited. Of the cells shown below, which one is likely to experience the greatest difficulty as it grows larger assuming it retains the same shape? This is...
  15. G

    Osmolarity of water in red blood cells?

    I am confused on how osmolarity of cells with water would cause a cell to swell, shrink, or burst. I know that a cell has a solution concentration of 300 mosm. In a lab that was done, we analyzed the impact of a red blood cell in solutions containing different osmolarities. For example, when a...
  16. L

    Test question: Respiring cells release CO2 into the bloodstream

    Test question: "Respiring cells release CO2 into the bloodstream..." 1. 2. For this question, I was thinking about the nature of CO2. It's not an acid or base, so how could it drop or raise the pH level?! So I put that the pH level won't change (B), but the real answer is C (it will...
  17. AnTiFreeze3

    Quadruple-Helix DNA Found in Human Cells

    Here is the full article, just published today: http://phys.org/news/2013-01-quadruple-helix-dna-human-cells.html The article makes it apparent that this discovery could be used to inhibit the reproduction of cancer cells. Does anyone know of any other uses that this discovery could lead to?
  18. E

    How does a photovoltaic cell convert light into electricity?

    i'm very interested in learning about photovoltaic cells, I've read in some sites already but they all describe it in very general way, can anyone tell me on detail how does it work? thanks
  19. B

    Determining efficiency of fuel cells

    Hi I need to compare solid working with \frac{1}{2}O_{2}+H_{2}O+2e^{-} \rightarrow 2OH^{-} and H_{2}+2OH^{-} \rightarrow 2H_{2}O+2e^{-} and liquid fuel cells working with H_{2}\rightarrow 2H^{+}+2e^{-} and \frac{1}{2}O_{2}+2H^{+}+2e^{-} \rightarrow H_{2}O My...
  20. K

    Efficiency Of Thin Film Solar Cells

    How does the efficiency of a Thin Film solar cell compare to the efficiency of a single crystal solar cell with reference to the 5 main solar cell parameters ( Iopt , Rs, Rsh, Is and n )? I know series resistance( Rs ) will probably increase in thin film cells because of grain boundaries...
  21. TheFerruccio

    Solar cells in parallel and series

    Hi, I am conducting an experiment whereby I have to measure the individual performance (on a per-cell basis) of solar cells on a solar panel. The panel has 20 cells, which are 4 strings in parallel of 5 cells in series each. The entire panel has a +V and chassis GND wire that I can open or...
  22. H

    Drug molecules binding to plasma cells?

    What problem arises or may potentially arise if drug molecules bind to plasma cells?
  23. G

    IPS cells via transgene free approach w/ small molecules

    Thought I'd share this article w/ everyone since I found it very interesting. Imagine being able to regulate stem cells without the need for genetic manipulation or growth factors etc. Small molecules are so much easier to work with. Very interesting...
  24. S

    Medical Do white blood cells increase or decrease in leukaemia?

    In leukaemia since immature white blood cells increase, do they overcrowd and decrease mature white blood cells. So does neutropenia and thrombocytopenia, leucocytopenia occur in leukaemia. Or does this deped on subtypes eg in some leukaemia B lymphocytes increase. Thanks :smile:
  25. O

    Force of kinesin molecule within cells

    Homework Statement Within cells, small organelles containing newly synthesized proteins are transported along microtubules by tiny molecular motors called kinesins. What force does a kinesin molecule need to deliver in order to accelerate an organelle having mass 0.028 pg from rest to 2.8...
  26. K

    I am a little stuck on an engineering question to do with Photovoltic cells.

    I need to calculate how much power will be generated by a solar cell at AM1.5. The cell is 1.5x3.5cm^2. I know that it is to do with the area of the cell i just don't understand how to work out the power generated without knowing things like the material. Any help would be appreciated.
  27. P

    Medical If I'm losing muscle mass , are some of my muscle cells actually disappearing?

    If I'm "losing muscle mass", are some of my muscle cells actually disappearing? I've been running a lot lately and losing weight. Mostly getting leaner, but recently I've started to worry about losing muscle mass. I used to lift weights a lot, but I haven't done that in a few months. If I keep...
  28. A

    Unraveling the Mystery of Biology: Understanding Cells

    I recently started studying biology because suddenly I started getting curious about this subject. I read about the cell theory which states that all living things have cells. Is this necessary - that all living things have cells? Can't they have some different structure? Also these type of...
  29. L

    Why would fuel cells be good for the economy?

    Congratulations, you've created a fuel cell car! Now you need electricity or fossil fuels to create hydrogen to fuel the car. So burn some coal to get electricity. How exactly does this help the environment again? What am I missing here?
  30. O

    Do mantle convection cells move?

    Hello, PhysicsForums! I've been discussing what little I know of plate tectonics with someone and the other party has suggested that convection cells within the mantle (assuming convection really occurs at all) should eventually move such that they no longer push more matter up through...
  31. H

    Why does the genetic composition of sex cells of an individual vary ?

    Why does the genetic composition of sex cells of an individual vary since the genome of an individual is same throughout his/her body.
  32. R

    Help in Understanding Hydrogen Fuel Cells?

    I'm doing a presentation on Hydrogen Fuel Cells for my class, but I'm having a hard time understanding how exactly it is that they work. I'm only able to find information on fuel cells and they tend to not be descriptive on the hydrogen part. If someone could please link some articles that...
  33. M

    Is the Carnot efficiency valid for fuel cells?

    So, I've read in books and on Wikipedia (see for instance http://en.wikipedia.org/wiki/Carnot%27s_theorem_%28thermodynamics%29#Applicability_to_fuel_cells_and_batteries) that the Carnot efficiency cannot be applied to a fuel cell because it is not a heat engine that produces work, operating...
  34. M

    Exploring Hydrogen Fuel Cells: Questions & Answers

    Homework Statement hi I've got to do a project for college and need some direction I want to know a few things more so if you can help let me know. some of the things include (if you could answer any it would be useful): why can't we make a longer electric current to harness all the...
  35. M

    PEM Fuel Cells vs Batteries: Understanding the Difference

    hi I've got to do a project for college and need some direction I want to know a few things more so if you can help let me know. some of the things include (if you could answer any it would be useful): why can't we make a longer electric current to harness all the electricity produced in a...
  36. Τ

    Calculate Cell Potential at 25°C for Fe & Pd Cells

    Homework Statement Calculate the cell potential at 25°C for the cell: Fe (s) | (Fe^2+ (0.100 M) || Pd^2+ (1.0*10^-5 M) | Pd (s) given that the standard potential for Fe^2+/Fe is -0.45 V and for Pd^2+/Pd is +0.95 V. A. +1.28 V B. +1.16 V C. +1.52 V D. +1.68 V Homework Equations E Cell...
  37. T

    Medical Article: Robot Reveals the Inner Workings of Brain Cells

    http://www.gatech.edu/newsroom/release.html?nid=128531 Browsing the alumni stuff, I see things that make me wish I were back in school. You kids and faculty are so lucky to be able to do this kind of stuff every day. I have serious envy! Alas, wife, kids, house, bills, argh. Nothing but work...
  38. M

    Optimizing Cell Suspension for Accurate Cell Counting

    I am an undergraduate physics student working in a biophysics laboratory, and recently on the job I have started culturing cells. We need the cells in suspension for reasons I can't disclose but the important part is that I am having some difficulties in the trypsinization process. The main...
  39. T

    Are humans a natural phenomenon if they are just society of cells?

    So a human is made of cells. It is essentially a city or society of cells that live together. There is no such thing as human, it's just a bunch of cells. So human is just a natural phenomenon, an emergent property. In addition, a cell is just a bunch of atoms. I.e. a collection of atoms...
  40. S

    Are Photovoltaic Cells Considered Ohmic Devices?

    Hey, I needed a clarification regarding this. Are photovoltaic cells ohmic devices? Or if I consider an entire PV Module, will that be an ohmic device or not? I basically need to know whether I can utilize the equation P = I2*R = V*I for a cell or not.
  41. J

    Conditional probability & r balls randomly distributed in n cells

    Conditional probability & "r balls randomly distributed in n cells" Homework Statement I'm posting this in hope that someone can give me a correct interpretation of the following problem (problem V.8 of Feller's Introduction to probability theory and its applications VOL I): 8. Seven balls...
  42. T

    Multicellularity and specialised lineage cells

    So the question is even though we may have some fair idea how multicellularity came about. How would this lead onto specialized line-aged cells in a multicellular organism ? For example differentiating to blood cells or bone cells. http://en.wikipedia.org/wiki/Multicellular_organism
  43. B

    Medical Can Stem Cells Taken from the Body Cure Colorectal Cancer?

    There are reports that stem cells have been successfully used to cure cancer in the lungs, spleen, brain and spine. It was done on a 38 year old man from Las Vegas, but can it cure colorectal cancer? And when was the stem cell cancer therapy first successfully tested?
  44. J

    Stem cells from infants for research

    So we use stem cells from infants for research, but do they never take those stem cells and use it to treat people, is it not possible to make cells from other people live in your body? would your body reject and kill those cells?
  45. G

    Total number of cancer cells inside a tumor: 100Each cell has a 10%

    Total number of cancer cells inside a tumor: 100 Each cell has a 10% chance of dying each time it divides The rate at which a cell leaves the mass is 1 every 8 hours The rate of division is 1 division / 2 hours whats the time needed to attain the 100 cells in the first place? What is the...
  46. N

    Medical Can we make stem cells from fat tissue?

    Please teach me this: I hear that we can make stem cells from fat tissue that is used in medical treatment.Is that correct? Thank you very much for your kind helping.
  47. G

    About magnet field in solid oxydes fuel cells

    Hello! I don't understand one easy moment in high temp solid oxydes fuel cells (SOFC): 1. Oxygen ions are moving always via solid electrolite ZrO2? SOFC without load and SOFC in short circuit modes. (High temp is default mean) 2. Electrolises process need electric energy and external...
  48. N

    Medical The difference between simple and complex cells

    Are complex cells in the brain physically different from simple cells or is the difference in their function/role?
  49. 3

    Salt Bridge & Voltaic Cells Experiment

    I did an experiment testing the thickness of a salt bridge (made of filter paper soaked in potassium nitrate) on the voltage produced from Zn and Cu half cells. This is similar to a thread someone made back in 2007. But I have no idea how to explain my findings or whether the thickness...
  50. E

    Why Asymmetrical Junctions are widely used in Solar Cells? What Advantages?

    Hello, I was investigating 'Asymmetrical P-N Junctions'. If the doping concentration of the P and N type semiconductors are different then the P-N junction they will form will be a asymmetrically doped Junction. I searched and come up with the fact that 95% of the solar cell structures are...
Back
Top