Microbiology Stories: Immunology

‏إظهار الرسائل ذات التسميات Immunology. إظهار كافة الرسائل

ELISA

ELISA

Simply ... it is a test to show the Ab-Ag reaction

Indirect:

To detect Ab.

Direct "Sandwitch":

To detect the Ag

Adhesion molecules

السلام عليكم و رحمة الله و بركاته

بعد اذنك يا دكتور اناعندي سؤال :

What is meant by :
adhesion molecules

الاجابة:
بسم الله الرحمن الرحيم

وعليكم السلام ورحمة الله وبركاته
بص يا سيدي
ببساطه دي عبارة عن مجموعة من البروتينات اللي موجوده علي سطح الخلايا المناعيه بتاعتنا
واللي ليها وظيفه مهمة جدا
ان هيا تربط ما بين الخلايا وبعضيها بقوه اثناء عملية تنشيط خلايا المناعه وتحفيزها ضد شئ غريب معين
بأسلوب تاني:

Adhesion molecules

Cell Adhesion Molecules (CAMs) are proteins located on the cell surface involved with the binding with other cells or with the extracellular matrix (ECM) in the process called cell adhesion.

خلينا نشوف اشهر نموذج ليها
وده اللي بيحصل اثناء عملية تنشيط ال T cells علشان تحصل عملية التنشيط دي لازم يكون في روابط كتيرة بين الخليه اللي بتقدم الAg
"Ag presenting cell" و ال T cell اللي هاتتعرف عليه خلينا نشوفها في الصورة ده هايكون اوضح

اتمني الاجابة تكون وضحت

في انتظار اسئلة اخري
د.احمد رمزي

Coomb's test

Coomb's test

Hypersensitivity Type I

Hypersensitivity Type I

"Immediate hypersensitivity reactions"

IgE mediated diseases

Mechanism of tissue injury:

Allergen stimulates Th2.

Th2 secrets: “IL-4” which stimulate B cell antibody class switching to produce IgE that binds to mast cell surface.

The Fc portion of IgE binds to the surface of mast cells.

When the allergen cross-links the Fab portions of the mast cell-bound IgE, this triggers degranulation.

Cross linkage of IgE on the surface of Mast cell:

يعني ببساطة:

القصة بتبدأ من ال Th2

هيا اللي بتفرز “IL-4” المسئول عن ال class switching of plasma cell to produce IgE insted of IgM
المشكلة ان ال IgE له مستقبلات علي سطح بعض الخلايا في الجسم زي ال Mast cells & Basophiles

في حالة ارتباط ال IgE بسطح هذه الخلايا تصبح حساسه "قابلة للانفجار" ....... sensitized

في حالة التعرض لل Allergen مرة اخري يرتبط بال IgE علي سطح الخلايا وهنا يحدث الانفجااااااار

Degranulation

See this movie:

1. Early phase:

Appears within minutes after exposure to the antigen.

Due to release of inflammatory mediators such as:

Histamine.
Platelet-activating factor.
Leukotrienes.
Bradykinins.
Prostaglandins.
Cytokines.

These inflammatory agents cause the following:

A. Vasodilatation:

This causes local redness (Erythema) at the site of allergen delivery.
If it is widespread, it can lead to a drop in blood pressure, and shock.

B. Increased capillary permeability:

This causes swelling of local tissues (Edema).
If widespread, it can lead to decreased blood volume and shock.
In Respiratory system, it causes broncho-constriction.
This leads to wheezing and difficulty in breathing (Asthma).

C. Stimulation of mucus secretion:

This leads to narrowing of airways (Asthma).

D. Stimulation of nerve endings:

This leads to itching and pain in the skin.

2. Late phase:

May begin several hours after exposure to antigen.

Due to release of Cytokines such as:

TNF.
IL-4.

These Cytokines stimulate the recruitment of leukocytes.

The principal leukocytes involved in this reaction are:

Eosinophils.
Neutrophils.

These cells mediate the contanous inflamatory reaction, which leads to destruction.

Clinical syndromes:

Two major forms are commonly encountered:

Localized & Systemic reactions

Localized reaction: "Atopy"

Hay fever.
Bronchial asthma.
Food allergies.
Dermatitis.

Systemic reaction: "Anaphylactic shock"

Diagnosis:

1. Skin test: "Prick & intradermal test"

Scratch test commonly used where antigens are topically applied on skin and skin scratches are made through them.

The tests resulting in wheal and flare.

2- Assay of Serum IgE:

Total IgE & Specific IgE.

Measured by enzyme immunoassay (ELISA).

IgE may be elevated in some non-atopic diseases (e.g., myelomas, helminthic infection).

Pictures showing Scratch test which used for diagnosis Hypersensitivity type I

Also it helps in treatment

Hypersensitivity

Hypersensitivity

Essential topic... base to understand many diseases you face in your practice

And commen question also you face in most of your exams

What is Hypersensitivity....?

Abnormal "exaggerated" immunological response due to failure of control mechanism, leading to tissue destruction.

يعني ببساطة...

Immune response زايد عن اللازم "وطبعا اللي يزيد عن حده ....ينقلب لضده"

وده فعليا اللي بيحصل

لأان الجسم بيحاول يعمل تصرف مناعي ولكنه يؤدي الي التكسير والدمار في الجسم بشكل عنيف غير مسيطر عليه

يا تري ازاي ده بيحصل...؟

باكتر من طريقة واسلوب "5 طرق تحديدا"

وعلشان كده عندنا 5 انواع من ال" Hypersensitivity "

4 منهم معتمدين علي وجود Ab كوسيط لعملية التدمير

وواحد منهم بس هوا اللي بيكون Cell mediated

خلينا بدأ ناخدهم واحد واحد ونفهم تفاصيلهم من حيث الميكانزم والتشخيص والعلاج كمان

Antibody Dependent Cell mediated Cytotoxicity "ADCC"

Antibody Dependent Cell mediated Cytotoxicity "ADCC"

Definition:

It is a mechanism of cell-mediated immunity whereby an effector cell of the immune system actively lyses a target cell that has been bound by specific antibodies.

It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection.

Classical ADCC is mediated by:

Natural killer (NK) cells.
Monocytes "Macrophages".
Eosinophils.

ADCC by NK cells:

NK cells are capable of antibody-dependent cellular cytotoxicity or ADCC. NK cells have receptors on their surface for the Fc portion of IgG. When the antibody IgG is made against epitopes on "foreign" membrane-bound cells, e.g., virus-infected cells and cancer cells, the Fab portions of the antibodies react with the "foreign" cell. The NK cells then bind to the Fc portion of the antibody.

The NK cell then releases pore-forming proteins called perforins, proteolytic enzymes called granzymes, and chemokines. Granzymes pass through the pores and activate the enzymes that lead to apoptosis of the infected cell by means of destruction of its structural cytoskeleton proteins and by chromosomal degradation. As a result, the cell breaks into fragments that are subsequently removed by phagocytes. Perforins can also sometimes result in cell lysis. (When NK cells are carrying out ADCC, they are sometimes also referred to as killer cells.)

Eosinophils can also mediate ADCC. For example, eosinophils can kill certain parasitic worms known as helminths through ADCC. ADCC is part of the adaptive immune response due to its dependence on a prior antibody response.

يعني ببساطة:
هي عملية قتل للخلية الغريبة عن طريق وسيط " اللي هوا ال Ab"
كل دور ال Ab انه يمسك الخليه الغريبة لكنه لا يستطيع فعل اي شئ اكتر من ذلك
ولأن لل Ab مستقبل "Fc receptor" علي سطح بعض الخلايا فممكن ان يرتبط بيها
يعني كده الا Ab هايكون ماسك الخلية الغريبة من ناحية "by Fab"
وماسك ال خلية اللي هاتقوم بعملية القتل من ناحية تانية "By Fc"
وده بيخلق اشارة قوية جوة ال NK يخليها تبدأ تفرز ما بداخلها لقتل الخلية الغريبة
Perforins.........خرامات تقوم بعمل فتحات في سطح الخلية مما يؤدي الي دمارها نهائيا
Granzymes........ عبارة عن مجموعه من الانزيمات اللي بتدخل جوه الخلية وتبدأ عملية ال Apoptosis
اما في حالة ال eosinophils فالوضع مختلف شوية
لأن الخلية الغريبة مش بتكون خلية واحده دي بتكون دوده في الاغلب
ولما بتحصل عملية الارتباط اللي حكينا عنها ده بيؤدي الي افراز ال eosinophils لكل محتوياتها القاتلة للدوده

The Fab portion of the antibody binds to epitopes on the "foreign" cell. The NK cell then binds to the Fc portion of the antibody. The NK cell is then able to contact the cell and release pore-forming proteins called perforins, proteolytic enzymes called granzymes, and chemokines. Granzymes pass through the pores and activate the enzymes that lead to apoptosis of the infected cell by means of destruction of its structural cytoskeleton proteins and by chromosomal degradation. As a result, the cell breaks into fragments that are subsequently removed by phagocytes. Perforins can also sometimes result in cell lysis.

To see interactive animation

Click the following link

http://student.ccbcmd.edu/courses/bio141/lecguide/unit5/humoral/abydefense/adcc/adccanim.html

والله الموفق
د.أحمد رمزي

Superantigen

Superantigen

Definition:
They are bacterial toxins or viral proteins that have the ability to bind to both MHC class II and TCR β chain outside the binding cleft.

Characters:

They do not need to be processed.
Able to activate all T cells irrespective of their antigen specificity.
They interact with MHC molecules outside the peptide binding groove.
Also bind with TCR β chain irrespective of antigen specificity.

Its effect:

Polyclonal activation of T cells.
They stimulate the release of abnormal large amounts of cytokines especially TNF.
It can lead to shock.

Examples:

Staphylococcal enterotoxin.
Staphylococcal toxic shock syndrome toxins (TSST).
Staphylococcal exfoliative toxin.
Streptococcal pyrogenic exotoxins.

MHC

السؤال كان عن ال MHC

عايزكم تركزو معايا قوي لأن الموضوع ده مهم جدا

وعلشان نذاكره كويس خلينا نعرف في الاول هوا مهم ليه؟

مهم لأنه بفهمنا لطبيعة ال MHC ودوره في الجسم

1. هانقدر نفهم ازاي الخلايا بتتعرف علي ال Ag وتبدأ تتفاعل ضده.

2. هانقدر نفهم ليه الجسم بيرفض الاعضاء الغريبة اللي بنزرعها كبديل لفشل الاعضاء "زراعة

3. وكمان هانقدر نفهم ليه العيان اللي عامل عملية زراعة اعضاء بيفضل ماشي علي ادوية تثبيط المناعة.

4. كمان هانفهم من خلاله ليه بتظر بعض الامراض عند سن معين وقبل كدة لأ " زي السكر والروماتويد وغيرهم...".

5. وبرده هانعرف ليه الجسم بيضرب الخلايا السرطانيه والخلايا اللي فيها فيروسات ويموتها بالرغم من انها خلايا جوه جسمي "self Ag" يعني بتاعتي مش غريبة عني....!

عامة خلينا نبدأ.....

Definition:

Histocompatibility antigens are self Ags; play a physiological role in Ag presentation and Transplantation.

Also, it is referred to HLA" human leukocyte antigens" because carry all types of HLA Ags in high concentrations.

MHC Genes:

The MHC genes present on the short arm of chromosome 6.

يعني ايه الكلام ده ؟

يعني ببساطة ان ال MHC عباره عن بروتين molecules بتكون موجوده علي سطح الخلايا بتاعتنا "بس مش كل الخلايا " الخلايا اللي عندها Nucleous بس

وده يا شباب بالظبط بالظبط زي فكرة البطاقة الشخصية...!

يعني ايه...؟

يعني مثلا ... مثلا... لو اي واحد فيا خرج من غير بطاقة هل ده ينفع؟

"طبعا البنات بيقولو عادي ومنهم اللي بيقولك انا اصلا ماطلعطهاش لسه"

بس الولاد فاهمني كويس

وفاهمين مدي الترحاب وحسن المعاملة والكرم اللي هايقابلوه من الظابط لما يكون مافيش بطاقه

وبيني وبينكم الظابط معذور

لانه هوا مايعرفش سيادتك مين

وبالتالي حقه انه يرحب بيك واوي كمان

نفس الكلام بالظبط بيحصل في الجسم

كل الخلايا بتاعتي "انا كاحمد مثلا" عليها بطاقة شخصية خاصة بيها مختلفة تمام الاختلاف عن البطاقة اللي موجوده عي خلايا مارك ومختلفه تماما عن البطاقة بتاعة عين او بتاعة ابو تريكة.

البطاقة دي حضراتكم هيا ال MHC molecules

وعلشان كده الجسم بيقدر يميز اي خلايا غريبة عنه ويتفاعل معاها ويقتها كمان ان لزم الامر " وده اللي بيخلي الجسم بيرفض الاعضاء الغريبة اللي بنزرعها كبديل لفشل الاعضاء "زراعة الاعضاء".

طيب يا دكتور انت قلتلنا ان الخلايا اللي عندها Nucleous بس هيا اللي عليها MHC

طب وخليه زي ال RBC ياتري وضعها ايه من الاعراب؟

اقولك يا سيدي

ببساطة... ربنا خلق ليه نوع مختلف من البطاقات بتميز خلايا احمد عن خلايا رامز

البطاقات دي اللي احنا بنسميها ABO grouping

علشان كده الجسم بيكسر كرات الدم الحمرا اللي منقوله ليه لو ماكانتش متطابقه مع الخلايا بتاعته.

هايسألني حد تاني مركز معايا وهوا بيقرا

هوا انت ليه يا دكتور معلم علي كلمة متطابقة..؟

لأنه ببساطة هيا دي مربط الفرس

تطابق الانسجة Histocompatibility

ماهو ال MHC اصلا اختصار لكلمة

Major Histocompatibility complex

يعني الجزئ المسئول عن تطابق الانسجة

كده نكون فهمنا معني الكلمة.

طيب يا تري هوا في منه انواع...؟

طبعا...

امال الفروق بنا وبين بعضينا هاتحصل ازاي؟

عندنا يا سيدي منه 3 انواع:

1و2و3

MHC Classes:

Class I molecules:

HLA-A, HLA-B, HLA-C.

Expressed on plasma membranes of most cells and tissues.

It presents Ag to CD8 cells "T Cytotoxic".

Class II molecules:

HLA-DP, HLA-DQ, HLA-DR.

Expressed on the surface of the Ag presenting cells including:

B lymphocytes.
Macrophages.
Dendritic cells.

It presents Ag to CD4 cells "T Helper".

Class III molecules:

Another type of MHC molecule.

Associated with certain complement components:

C2, C4 & factor B, also with TNF α and β.

These Ags have no role in graft rejection.

لو واحد قرأ من غير تركيز هايسألني:

طيب يا دكتور ازاي هزوا 3 انواع بس وبيخلي فيه اختلاف بينا "يعني مافيش اتنين متطابقين تماما"

اصل لو هوا 3 انواع بس يبقي كنا هانلاقي في كل 4 اتنين زي بعض..؟

طبعا ده كلام كويس

معناه ان سيادتك ركزت في العربي وبس

وماركزتش في اللي مكتوب تحت العناوين بالنجليزي...!

ببساطه

أول نوع "Class I"

فيه منه 3 اصناف "A,B,C"

والنوع التاني "Class II"

فيه منه برده 3 اصناف "DP,DQ,DR"

لأ ومش بس كده

ربنا سبحانه وتعالي خلق من كل صنف من دول اشكال مختلفة جدا

يعني مثلا ....

MHC class B عندها اكتر من 300 شكل وزيها الباقي

وده يخلي فيه استحاله ان اتنين من البشر يكونوا شبه بعض

Most of the HLA genes are polymorphic:

Multiple alleles occur at a single HLA locus.

(Alleles = alternate forms) that represent small variations in the nucleotide sequence of the gene.

That means: There are many alternative versions of each MHC gene that yield proteins with slightly distinct sequences.

For example:

HLA-A: more than 400 alleles.
HLA-B: more than 300 alleles.

طبعا هايجي واحد دلوقتي ويسألني انت بتشرح في ايه اساسا...؟

السؤال كان عن ال MHC وانت عمال تقول HLA....؟

والاجابة ببساطة انهم الاتنين حاجه واحد "علشا ن ماتلخبطوش نفسيكم"

لأنهم اول ماكتشفو ال MHC اكتشفوه علي سطح كرات الدم البيضاء " leukocytes"

وعلشان كده سموها علي اسمها في الاول "لأنهم ماكنوش عارفين دورها في تطابق الانسجة"

Human Leukocyte Antigens (HLA)

ياتري لازمتها ايه بأه "شغلانتها ايه ياعني"..؟

1. قولناها " تطبق الانسجة".

2. ليها دورمهم جدا في عملية تعريف الخلايا المناعية " T&B lymphocytes" بالخصم بتاعها اللي مطلوب منها تخلص عليه

لأن الخلايا الاكولة اللي بتقدم الخصم الغريب ده "APC"

بتحتاج حاجة "مشبك مثلا" تمسكه بيه علشان تعرف خلايا المناعة عليه

ومن غير الحركة دي مش هايحصل تنبيه للقوات الخاصة بتاعة المناعه

3. لقينا كمان انه ليه علاقه ببعض الامراض الوراثية ذات الاصل المناعي زي الروماتويد مثلا

الروماتويد ده اصلا مرض سئ جدا بيضرب المفاصل

وبيظر تقريبا في سن التلاتينات, وجدوا انه بكون في نوع معين من ال MHC بيظهر وبيكتر أوي في الجسم بتاع المريض

يبقي اكيد في علاقة...!

" بيني وبينكم تخيلوا كده واحد عنده تلاتين سنه او اكتر... خلايا المناعه بتاعته عارفه ان خلايا المفاصل بتاعته برده ماعندهاش MHC class II DR4

واذ فجأة يظهر الجزئ ده علي خلايا المفاصل .... ساتها جهاز المناعه يشوفها كخلايا غريبة ويدا في التفاعل ضدها " وهنا يحصل المرض.

وكده نكون فهمنا الموضوع

فاضل حاجه بسيطة خالص ...

ان احنا نعرف ان الجينات المسئولة عن تكوين ال MHC موجوده عندنا علي الكروموسوم رقم 6 تحديدا علي الدراع القصير منه

وبكده اكون ان خلصت

هاستني اسئلتكم وتعليقاكم وسامحوني ان كنت قصرت

والله الموفق

د.أحمد رمزي

Apoptosis due to Fas liganed - Fas pathway

A nice trial.......to understand chemotaxis

A nice trial.......to understand chemotaxis

But DON'T worry...your neutrophils doesn't make this voice

!!!!!!!

Phagocytosis

A very interesting video of phagocytosis......hehehehehehehe

Exotoxins

Definition:

Protein toxins usually secreted from a living bacterium but also released upon bacterial lysis.

Exotoxins divided into three types on the basis of their structure and activities:

A-B toxins.
Membrane disrupting Toxins "Cytolytic enzymes".
Superantigens.

(1) A-B toxins:

These toxins-interfere with cell metabolism.

Each is formed of two portions:

Portion A:

 It is the enzymatic portion of the toxin.

 It is translocated into host cells after binding of B portion.

Portion B:

 Binds to specific host cell.

Binding and Entry of an A-B Toxin

A-B toxins consist of two parts, an A (active) component and a B (binding) component. The B component of the exotoxin binds to a receptor on the surface of a susceptible host cell. The exotoxin now enters the host cell, in this case by endocytosis, and causes harm by inactivating a host cell target protein through ADP-ribosylation.

Examples:

Diphtheria exotoxin, produced by Corynebacterium diphtheriae.
Cholera exotoxin, produced by Vibrio cholerae.
Botulinum exotoxin, produced by Clostridium botulinum.

(2) Membrane disrupting Toxins "Cytolytic enzymes":

This class of exotoxin lyses host cells by disrupting the plasma membrane.

Two kinds are known:

One is a protein that forms pores in the membrane causing leakage of cytoplasm and water entry.

The other acts as phospholipase.

These toxins are general cytotoxins because they can affect any host cell.

However, they are also referred to as "hemolysins" due to their effect on erythrocytes, which are a convenient model of their actions.

Examples:

Listeriolysin: it is a pore-forming cytotoxin that is produced by Listeria monocytogenes.
Lecithinase: it is a phospholipase that is produced by Clostridium perfringens.

(3) Superantigens:

Bind directly to the outside of MHC-II molecules and are recognized by many CD4 T-lymphocytes.

This non-specific activation of very large numbers of these lymphocytes results in a release of large amount of interleukin-2 and other cytokines, leading to shock.

Examples:

Toxic shock syndrome toxin-1 (TSST-1) which is produced by staph.aureus.
Erythrogenic toxin which is produced by Streptococcus pyogenes.

Complement Activation

سؤال عن ال

Pathwayes of activation of complement

Complement protiens are soluble protiens present in all of our body fluids "except CSF & Urine".
It present in inactive forms, so needs activation to work proberly.
The activation process occures by diffrent pathways:
3 pathways actually:

Classical pathway.
Alternative pathway.
Lectin pathway.

These are many pictures showing the diffrent pathways of complement activation:

Let us to discuss each pathway ......

Classical pathway:

Assembly of C1 during the Classical Complement Pathway

The Fab of IgG or IgM bind to epitopes on an antigen. C1q, C1r, and C1s then assembles on the Fc portion of the antibodies to form C1, the first enzyme of the classical complement pathway. The enzyme C1 is able to cleave C4 into C4a and C4b, as well as C2 into C2a and C2b.

Formation of C3 Convertase during the Classical Complement Pathway

The enzyme C1 is able to cleave C4 into C4a and C4b. The C4b binds to adjacent proteins and carbohydrates on the surface of the antigen. C2 then binds to the C4b and C1 cleaves C2 into C2a and C2b. The C4b2a functions as a C3 convertase that can subsequently cleave hundreds of molecules of C3 into C3a and C3b.

Formation of C5 Convertase during the Classical Complement Pathway

The C4a2b functions as a C3 convertase that can subsequently cleave hundreds of molecules of C3 into C3a and C3b. Much of the C3b binds to adjacent proteins and carbohydrates on the antigen to participate in opsonization while C3a can stimulate inflammatory responses. Some of the C3b binds to C4b2a to form C4b2a3b, a C5 convertase that can cleave C5 into C5a and C5b.

The Membrane Attack Complex (MAC) Causing Cell Lysis

This C5b6789n, or membrane attack complex (MAC), puts pores into lipid bilayer membranes of human cells to which antibodies have bound. This results in cell lysis. MAC can also damage the envelope of enveloped viruses and put pores in the outer membrane and cytoplasmic membrane of gram-negative bacteria causing their lysis.

See these links:

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/c1act_flash.html

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/c3case_flash.html

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/c5case_flash.html

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/mac_flash.html

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/cytogn.html

Lectin pathway:

Activation of the Lectin Pathway

Activation of the lectin pathway begins when mannose-binding protein (MBP) binds to the mannose groups of the carbohydrates on microorganisms. Two more lectin pathway proteins called MASP1 and MASP2 (equivalent to C1r and C1s of the classical pathway) now bind to the MBP. This forms an enzyme similar to C1 of the classical complement pathway that is able to cleave C4 and C2 to form C4bC2a, the C3 convertase that is able to enzymatically split hundreds of molecules of C3 into C3a and C3b.

See this link:

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/lectin_flash.html

Alternative pathway:

Activation of the Alternative Complement Pathway and Formation of C3 Convertase

Activation of the alternative complement pathway begins when C3b (or C3i) binds to the cell wall and other surface components of microbes. Alternative pathway protein Factor B then combines with the cell-bound C3b to form C3bB. Factor D then splits the bound Factor B into Bb and Ba, forming C3bBb. A serum protein called properdin then binds to the Bb to form C3bBbP. C3bBbP functions as a C3 convertase that can enzymatically split hundreds of molecules of C3 into C3a and C3b.

Formation of C5 Convertase during the Alternative Complement Pathway

Some C3b binds to C3bBb to form C3bBb3b. C3bBb3b functions as a C5 convertase that can enzymatically split hundreds of molecules of C5 into C5a and C5b.

See this link:

http://student.ccbcmd.edu/courses/bio141/lecguide/unit4/innate/alternative_flash.html