Biology Unit 3 Questions Megathread

[Drunk]

Why do lymph nodes swell up?

I'm guessing that due to an infection the node will have more macrophages and lymphocytes, so they'd need get larger to accommodate them all. Also as another guess, they could be infected themselves and inflammation could occur in the node?

Hmm, well it's in response to a question from 2006 VCAA - there was a graph showing, between a specific time period, an increasing HIV concentration, with decreasing T-cell concentration and it asked to explain the swelling of the lymph node during this time period

[WhoTookMyUsername]

what is the difference between lymph gland and lymph node, does lymph gland have some sort of duct? what is an example of lymph gland?>

[Russ]

Same thing.

Swollen nodes are caused because you get an infection and you get excess transport to the LNs and cell migration. It's only really a problem with serious overinfection (ie HIV). It won't happen from just a cold or similar

[Truck]

Why do lymph nodes swell up?

I'm guessing that due to an infection the node will have more macrophages and lymphocytes, so they'd need get larger to accommodate them all. Also as another guess, they could be infected themselves and inflammation could occur in the node?

Hmm, well it's in response to a question from 2006 VCAA - there was a graph showing, between a specific time period, an increasing HIV concentration, with decreasing T-cell concentration and it asked to explain the swelling of the lymph node during this time period

I just checked the '06 assessment report and it just says 'answer needs to relate to their role within defense mechanisms against infective agents'... so I think my first answer was right as the lymph node is where macrophages go to present the pathogens they've ingested etc.... and bazza, afaik lymph gland is the same thing as lymph node.

edit: russ beat me to it =D

[epinephrine]

Could someone please explain the difference between MHC 1 and 2 markers and do
B and T cells recognise other cells with the same MHC 2 markers ? I'm still a bit
confused 

[lexitu]

Could someone please explain the difference between MHC 1 and 2 markers and do
B and T cells recognise other cells with the same MHC 2 markers ? I'm still a bit
confused 

MHC I proteins are found on all/most body cells and are unique to that person so can be classified as self. Fragments of proteins synthesised within the cell are constantly being attached to these MHC proteins - so these MHC I proteins are able to display self-antigens. If a pathogen is to enter that cell and start producing substances then fragments of these substances will be displayed on the MHC I proteins of that cell - i.e. the MHC I proteins are displaying non-self antigens. This allows cytoxic T cells to bind to both the self-MHC I protein and the non-self antigen that it is displaying - there has to be double recognition - recognition of a self-protein (but not antigen) and recognition of a non-self antigen.

So, don't let MHC proteins confuse you. Cells have MHC class I proteins. When these are loaded they either display self-antigens or non-self antigens. If a cytotoxic T cell recognises the non-self antigen bound to an MHC class 1 marker then an immune response is initiated.


Class II MHC proteins are found only on surfaces of antigen presenting cells - the proteins loaded onto these MHC proteins are not produced within the cell but rather are phagocytosed, broken down, and then fragments are displayed on the MHC II proteins. Helper T cells are generally the only cells to bind to MHC II proteins and the non-self antigens that they are displaying. It's not the B cells that recognise these proteins and the antigens because they themselves are professional antigen presenting cells.

[WhoTookMyUsername]

EDIT: i just realised i don't really know much about the non - specific (e.g.  non IgE) inflammatory response and how this occures, can someone elaborate? 

 histamines cytokines?

and how do general inflammation of the body occur (e.g. non - specific) is this just due to serotonin and histamine release from macrophages / basophil cells?

EDIT
1) can mast cells release histmanine without specific activation and how/
2) wtf is serotonin lol, i saw it mentioned as being released by mast / basophils, but i looked it up and there doesnt' seem to be info about serotonin / inflammatory response

EDIT 2: Is DNA present in nucleolus as well, and does the nucleolus hold tRNA and mRNA?

Thanks

[lexitu]

^ I'll get back to you on this (or let one of the VN experts answer this) but I think you might have confused yourself here - the vast majority of inflammatory responses are non-specific. I think it's just contact that promotes histamine release.

DNA isn't present in the nucleolus (at a simple level) and no, talk about rRNA not the others.

[Russ]

Inflammatory responses aren't specific to a pathogen, bacterium X (s. aureus) can cause the same response as bacterium Y (s. pneumoniae). You get cytokine mediated vasodilation and upregulation of specific receptors/ligands on the blood vessels to allow leucocytes to stick. When they stick they migrate into the tissue. That causes the 4 typical inflammation signs (heat/swelling/soreness/redness).

The cytokines tend to originate from tissue resident macrophages.

RE: mast cells, depends what you mean by specific activation. They have IgE on the cell surface, which is obviously specific, but a mast cell isn't specific for a single pathogen. On activation, they secrete preformed histamine and start synthesizing lipid mediators (prostaglandins) and cytokines (TNFa, IL1 etc.).

I don't think you need to know any of that though.

Never heard of serotonin as a major inflammatory mediator, a quick look at the wiki article says it will affect blood vessels and a quick google says that inflammation decreases serotonin levels but not the other way around

[WhoTookMyUsername]

do all WBCs (e.g. macrophages) release the cytokines to cause inflammation?

Histmaine is not involved in non - specific activated response?

still a bit confused

okay, this is what i think is happening

infection occurs, macrophages and other phagocytes engulf pathogen, these release cytokines that include various interleukins which promote inflammation, pyrogens that raise temperature, but NO histamine ? ( or is histmaine released in small amounts by phagocytes etc. as well? )

This then causes vasodilation, permeabiliyt etc.

and Mast cells are activated by a specific antigen, and each mast cell has many of the SAME receptors

?
lol

thanks!

[Charmz]

Its actually that the bacteria crosses your first line of defence causing mast cells to release histamine which cause the capillaries to dilate and this causes phagocytes to diapedise through the capillary and engulf foreign bacteria. Cytokines are released from the area where the activity is happening. The Khanacademy dude explains it exceptionally well.
http://www.khanacademy.org/video/inflammatory-response?playlist=Biology

Histamine are a part of the non-specific immune system as well as mast cells. They are activated by the substances released by the pathogen or from the chemokines released by the skin cells.

[WhoTookMyUsername]

sweet, so mast cells can be activated by cytokines + chemicals from bacteria, not only IgE activation!
Do basophils release histamine as a result of the same stimulus?
Do macrohpages release any cytokines?


http://img32.imageshack.us/img32/2793/gfdgfd.png
can anyone confirm the logic behind B - is it because the signal PASSEs to the interneuron, but does not initiated an action potential?


thanks


if vcaa

[epinephrine]

Hmmm.....I thought that it would generate an AP in the sensory neuron and as a result passes to
the interneuron but is not able to reach the threshold for the motor neuron. Thus you could
definetly eliminate D,C and A as B is simply the best answer  

Hope that helps

[Russ]

and Mast cells are activated by a specific antigen, and each mast cell has many of the SAME receptors

Mast cells have multiple receptors.

Do basophils release histamine as a result of the same stimulus?
Do macrohpages release any cytokines?

Yes/Yes.

can anyone confirm the logic behind B - is it because the signal PASSEs to the interneuron, but does not initiated an action potential?

Yes, if neuron X activates it will release neurotransmitters regardless of whether it's sufficient to activate the subsequent neuron

[Kaille]

how does a fever occur?

Heinemann says the infected cells release pyrogens that cause the hypothalamus to increase the set temperature but other texts, biozone in think says that the infected cells release interleukin 1 that travel to the brain causing it produce prostoglandins resulting in the hypothalamus increasing the set temp...

which is more correct?