Hypersensitivity, Overview of the 4 Types, Animation.

(USMLE topics) Basics of hypersensitivity, symptoms, causes, summary of mechanisms of action the 4 types.
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Hypersensitivity refers to abnormal reactions of the immune system against certain antigens. It includes exaggerated reactions to otherwise harmless environmental antigens, commonly known as allergies; and inappropriate reactions against the body’s own antigens, or autoimmune diseases.
Reactions can range from a mild rash, to damaged organs, to fatal anaphylactic shock.
There are 2 principal groups of factors contributing to hypersensitivity:
- Imbalance between effectors and regulators of immune response: in some people, mechanisms that normally moderate the immune system are compromised, causing it to overreact to harmless, non-infectious antigens.
- Self-reactivity of immune cells: during their development in the thymus and bone marrow, T-cells and B-cells learn to not react to the body’s own antigens; self-reactive cells are normally eliminated; but in some people, some of these cells escape and may attack their own tissues once activated.
Hypersensitivity reactions only occur in pre-sensitized individuals. Patients must have had a previous contact with the antigen, which produced no symptoms, but during which the body had started making antibodies or activated immune cells that may cause symptoms in subsequent exposures to the same antigen.
Hypersensitivity is classified into 4 types based on mechanisms of action:
In type I hypersensitivity, a previous exposure to the antigen results in production of a class of antibodies called IgE. IgE molecules bind to their receptors on the surface of mast cells and basophils. Upon re-exposure to the same antigen, or sometimes a similar antigen, the antigen binds to adjacent IgE molecules, bringing their receptors together, triggering a signaling cascade that induces the release of histamine and other inflammatory chemicals. These chemicals cause dilation of blood vessels, smooth muscle spasms, and are responsible for symptoms such as edema, rash, difficulty breathing due to bronchospasm, abdominal cramping, vomiting and diarrhea. The reactions are immediate, within minutes of contact with the antigen, and can range from mild to severe. Severe reactions may lead to anaphylactic shock, a life-threatening condition in which blood pressure drops and airways narrow to a dangerous level. Most allergies are type I hypersensitivity reactions.
In type II hypersensitivity, previously formed IgG or IgM antibodies bind to antigens on the surface of a particular cell type. Antibody binding marks the cells for destruction, either by the complement system or phagocytosis. The antibodies may also interfere with normal functions of the cells without killing them. Type II is at the basis of many autoimmune diseases, where the body produces antibodies to destroy its own cells. Another example is hemolytic disease of the newborn, where maternal antibodies bind to D-antigen on the surface of fetal red blood cells and destroy them.
Type III hypersensitivity reactions are also mediated by IgM or IgG, but in this case, the antibodies bind to free-floating antigens, forming antibody-antigen complexes. The complement system is activated and inflammation results, causing damage to the affected tissue. A typical example is serum sickness, induced by a large amount of antigens in the blood. Immune complexes are deposited in the walls of blood vessels, triggering their inflammation, or vasculitis.
Type IV hypersensitivity is a delayed reaction, mediated by T-cells. Pre-sensitized T-cells are produced during a previous contact with the antigen. Upon re-exposure to the same antigen, T-helper cells release inflammatory cytokines, while T-killers induce cytotoxic reactions. Typical examples are allergic reactions to substances that come into direct contact with the skin, known as contact dermatitis. Type IV is also the basis of the tuberculosis skin test.

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[@adeyemibabatunde1814]

Which type is involved in irritable bowel syndrome?
Are gut allergy and leaky gut real and what type of hypersensitivity is involved?

[@mutsamakaza6908]

i watched this video this morning and i felt like the queen of hypersensitivity when i was writting my inclass test about it

[@its_fact_shorts4870]

Queen 😂😂😂

[@renereeb1351]

Wow! This is the perfect explanation, very clear and summarizes the most important parts of each type. Taught me what I tried to learn for an hour and a half in 5 minutes.

[@sanjanajain7672]

True

[@annellengassa6884]

literally

[@P_H_O_N_K_R_A_D_I_O]

This is almost impossible to study for a suppressant or a cure cause it's so rare to occur in ppl an it's even more rare for animals. Cause if you could come up with a suppressant or a cure you'd make big fuckin bucks mannee

[@mohammedozairarif7000]

As perfect as it can get. Great work!

[@berilalbayrak7524]

It was more helpful than my professors 3-hour-long classes thank you

[@Alilamedicalmedia]

You're very welcome!

[@adeyemibabatunde1814]

​@@Alilamedicalmedia
Which type is involved in irritable bowel syndrome?
Are gut allergy and leaky gut real and what type of hypersensitivity is involved?

[@faialnashmi4710]

This was such a helpful recap! THANK YOU

[@dr.dorukerdem]

Very useful and comprehensive video but I wish every single examples of the types of hypersensitivities are shown in this video. I liked it, waiting more videos like this

[@hayatahmed420]

As usual short and brief. thank you so much

[@zeinabghamlouch9920]

very well explained, thank you so much!

[@Aestheticalien.]

Perfect! Clean! Excellent! Simple explanation.. thank you so much 😄❤

[@oratilemoloi556]

Thank you for this video now I understand inflammatory, auntoimmune and allergic disorders a lot more

[@Jeene269]

Short and sweetly explained 😍

[@whbajeel9181]

Thanks a lot. Perfect explanation.

[@hemnahmad7822]

its made me crazy🤩really amazing explanation. go ahead👏

[@miranmuslem]

Amazing video! Thank you!

[@drahmedmohamed7779]

thnks for Alila medical media i hope to get more video like this

[@mishamalghani7955]

Very well explained 👏

[@shahwaliafghan102]

thanks for your efforts .this video and all of videos on this chanel are so helpful.
please do a video on birth asphyxia.
thanks

[@user-pq7uy6tp3c]

amazing video! everything is explained right! thnak you!

[@karibaddie8684]

This explained to me very well. ❤

[@shaiklathifmunnisha1426]

Tq so much very crystal clear explanation

[@ayat4522]

superb...its so helpful in making difference of these four only in few minutes

[@Alilamedicalmedia]

Happy to help

[@anam543rnaz3]

Perfect explanation

[@thacompilations4010]

Clear and concise

[@faash8964]

amazing! precise and great!!
God bless you

[@missingaisaaya2148]

Precise and educative

[@niazwali8169]

great and nice lecture very helful

[@omniloop7232]

It's so helpful 👍🏼

[@prwsharosarian2336]

Alila is the best

[@rehanullahsajan]

Thank You.🙏🏻

[@FriendlyPrinter]

That was helpful, thanks

[@BaoTran-ls7oy]

Thank you for the video!
Are antibodies able to bind to everything it chooses including cell receptors, antigens, etc.?

[@rianeon]

HT - abnormal immune system reactions against specific antigens.
involves excessive immune reactions to harmless antigens (allergens) and autoimmune reactions - immune responses against self-antigens.
- reactions can vary from minor rashes to serious anaphylactic shocks
Cause
- self reactivity - during lymphocyte development - the B and T cells undergo various pathways that ensure that they do not react to self-antigens, and self reactive lymphocytes are eradicated. However sometimes some self reactive lymphocytes remain. and upon activation, they could mount an attack directed to the persons tissues.
HT reactions only take place when the person has previously been exposed to the antigen, during which the body has created antibodies against the antigen or activated lymphocytes.
HT divided into 4 types - have their own defining mechanism of action
(most allergies are type 1)
1) first exposure to antigen -> IgE production by B cells -> attach to receptors (via Fc region) on the surface of mast cells. (the rest on my notes) chemicals released by histamine -> result in difficulty breathing due to bronchoconstriction.
re-exposure -> reactions to antigen present immediately -> reactions can be mild e.g. severe e.g. anaphylactic shock - life threatening -> narrowing of airways and lowered blood pressure (epipen needed)
2) (IgG/IgM mediated) previously formed IgG or IgM (prod after first exposure)- bind to antigens on cell surface -> this antibody binding act as markers for the cells to be destroyed via complement or phagocytosis (called ADCC)
- it is a cause of a lot of autoimmune diseases for example hemolytic disease of new born: D-antigens on the surface of fetal erythrocytes are bound by maternal IgG/IgM -> these red blood cells are destroyed.
3) IgG/IgM mediated - bind to soluble antigens -> forming antibody-antigen immune complexes -> complement system is activated -> inflammation -> tissue damage
e.g. serum sickness - presence of a lot of antigens in the blood -> antibodies bind to antigens - form immune complexes -> deposition into the blood vessels. -> inflammation of blood vessels.
4) T cell mediated - previously sensitised T cells are re-exposed to the exact antigen. T helper cells release inflammatory cytokines whereas // cytotoxic t cells - release perforin and granzymes -> apoptosis
e.g. T4 are basis for skin contact allergic reactions such as contact dermatitis ->
skin tests like those for tuberculosis

[@drprocrastinate4719]

Thx mate 🙏

[@mulkiali9439]

thank u. great simple summary

[@adeyemibabatunde1814]

Great summary

[@annamarianalumansi3178]

GREAT VIDEO

[@1412Z]

Thank you so much

[@Bamdeidz]

Perfect amazing flawless

[@rub9729]

much better than my teachers

[@thembbsvibes]

Thank You ❤

[@favourobasi5012]

Thank you

[@NaveenKumar-pj6xn]

Thanks a lot

[@joannadaniel9396]

thank you

[@pepayuchengco7187]

Thank youu❤❤❤

[@ngosandhlovu7037]

Kindly do a full explanation of asphyxia neonaturum please

[@pavankumar-ln4ks]

Very nice 👌

[@masungamkangala6337]

This was so helpful dear🥺

[@Alilamedicalmedia]

Glad you think so!

[@Lovefornature555]

Nice video ❤️

[@bravekhan2654]

Thank u soo much

[@Domino00089]

I have a question??
When the macrophages present the allergens which are non self antigens don't they engulf them to certain small antigen peptides that are displayed on their surface?
How do they further (the allergens) go on to react on the mast cells if they are already processed.

[@prasannak3439]

Perfect ❤

[@DR.NHR1]

Thanks

[@lucilaalvarez4095]

Nadia are you aware Che killed many innocents? And participated in the creation of forced labor "concentration camps" in Cuba?

[@zmzmcardp]

Easified 🙌🏻

[@user-ch9ng3no9m]

Love this way 😍 thank you bae❤️

[@LugandaLearner]

Awesome 🇺🇬

[@fatehaarshi9163]

Thank u so much ..😭😭😭

[@muhammadumairmuhammadumair4174]

G thnks

[@proteen530]

Please try to reduce the opacity of thr water mark in the video... @copyright thing

[@drhyarapremiumskincare181]

Good vdo
Please permit me to use for give knowledge to other people Thank you

[@Alilamedicalmedia]

You may link to our videos but you may not download them for independent use without purchasing a license. Thank you.

[@rai_sworld]

Is this imminologic reactions?

[@amosmoeti728]

well explained. but type 3 hypersensitivity is mediated by IgA and IgM, NOT IgG/IgM.

[@Alilamedicalmedia]

Hmm, look again! www.sciencedirect.com/topics/medicine-and-dentistry/type-iii-hypersensitivity
www.ncbi.nlm.nih.gov/books/NBK559122/

[@NyanRainbowz2010]

I don't understand, it says on Google hypersensitive also means the sensitivity of skin aka what I have where I absolutely cannot stand the feel of dry stuff

[@afal5547]

you are the god

[@medicallifewithjohn]

Nice

[@ajaypalkandu1583]

Need videos of diabetes mellitus

[@Alilamedicalmedia]

Look for it in our channel!

[@lanaw7304]

Hi im a 24yrs old female ...... before thisyear i exprienced no allergy to paracetamol , flueout , neorgesic and i have used all of them !! but this year i exprienced allergy to flueout , neorgesic , and doliprane 1000mg ( hives and severe body neck face itching, but for the doliprane 1000mg was very severe itching that i couldnt stand and got hydrocortizion and desloratadine to supress it ... i was never like that before before this year sometimes ive taken 2 (1000mg) together but no problem happened i dont know whats the problem with me ...

[@adeyemibabatunde1814]

Go to hospital
See a doctor

[@user-gz9wm7rb9c]

💙

[@alaamohammed5277]

WOOOOW :)

[@proteen530]

Water mark is disturbing to read

[@adeyemibabatunde1814]

Which type is involved in irritable bowel syndrome?
Are gut allergy and leaky gut real and what type of hypersensitivity is involved?

[@Aestheticalien.]

Type 1 hypersensitivity I guess

[@niazwali8169]

please contineuse the video as soon as possible to upload

[@narendraprasadmp6972]

Ķkkk
Llllĺĺ
0p
.
Lhuóyy0kl

[@miladmehrbod5289]

the watermark is too visible!!!

[@ummehafsa4096]

OMG😳

[@MOSTAFA_lkii]

حي الله جماعة كلية بغداد

[@sugabay]

So can I have a normal pregnancy with type 2 ? I had a early miscarriage before I knew I was hypersensitive

[@amosmoeti728]

there is likely hood of you having Rh imcompability in your future pregnancy if your last fetal loss was due to systemic hypersensitivity. make sure you receive a dose of anti D as early as possible on your next pregnancy

[@timekillerinfotainment869]

I didn't understand! Disliked. Sorry!

[@kkm.9741]

#official_tella

[@sayidhussein7042]

Thank you