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IMMUNITY

introduction -immunity is a protection power of human body against infectious  that is called immunity. immunity protect from foreign material. immunity produced resistance   against microorganisms and their product.  immunity help to protect from infectious disease in normal language immunity is the host defense system.

definition -

'immunity is the capability of the body resist harmful microbes ''

'immunity is the biological defenses to avoid  infection , disease ,or other unwanted biological invention ''

''immunity is define as immunity is the ability of an organism fight against disease and pathogens or immunity is a self defense mechanism of human body against pathogens or disease ''

                        

                     

              

Classification Of Immunity Or Types 

(1) immunity divided into two types 

• innate 
• acquired 

(2) innate immunity divided into two types 

• specific 
• nonspecific  

(3) acquired immunity divided into two types 

• active immunity 
• passive immunity 

(4) active immunity  divided into two types

• natural 
• artificial 

(5) passive immunity  divided into two types 

• natural 
• artificial 

(1) Innate immunity - innate immunity is a natural immunity which may be genetically passed on from one generation to other generation. innate immunity is know as birth immunity innate immunity present in individual from birth. innate immunity is commonly  divided in to two types.

1. specific immunity 
2. nonspecific immunity 

1. specific immunity - we know specific immunity is a type of innate immunity but it is not present from birth because this immunity develop in individual against specific antigen.  basically the immune system produced millions of lymphocyte and each lymphocytes has different antigen receptor. specific immunity show difference between self cell and foreign cell. its can recognize foreign cell and ignore self cell. example of specific  immune system its remember pathogens encounter such as chicken pox. chicken pox is a infection that dose not occur once in humans once again.

2. nonspecific immunity - non specific immunity is a safety system of our body which protect the human body from infectious diseases, mainly involves all the mechanisms  of our body such as skin  , gastrointestinal tract, genitourinary tract, respiratory tract, mucous membrane, eyes etc. the various non specific mechanisms are present they are following -

• Skin 
• Mucus membrane 
• Respiratory tract 
• Gastrointestinal tract 
• Genitourinary tract 
• Eye 

• Skin - skin is a barriers of all pathogens because skin is cover the body and provide protection against invading microorganism,they provide mechanical barriers. sink is consist of the  epidermis, dermis, and basement membrane. epidermis is outermost  layer of body  and from protective barriers cover the body surface and other function of skin is regulate the body temperature, sensory function etc.

•  Mucus membrane - mucus membrane are present in various body system such as  genitourinary, urinary, respiratory, gastrointestinal and all other systems of body prevent from invasion of pathogens or microorganism. the mucus membrane make protective covering for body and make trap for microorganism.

• Respiratory tract -   respiratory tract start from nose and microorganism firstly enter in nose through air but nose structure prevent  entry of microorganism because nasal hair and mucus secretion trap particle. they microorganism enter in nose and held at mucus lining and the epithelium and sent to pharynx where coughing and sneezing help removal of microorganism from respiratory tract .    

• Genitourinary tract -  urine PH and the flushing action of urine eliminate so many microorganism. the vaginal secretion are highly acidic due to formation of glycogen by lactobacillus. acidity of vagina make if unfavorable condition for the growth of microorganism     

• Gastrointestinal - saliva secretion by salivary gland, saliva help to control growth  microorganism and stomach is highly acidic , acidic condition of stomach inhibits multiplication of microorganism and mucus membrane present in digestive tract they protect from infection . 

• Eye - secretion of tear by lacrimal gland  protect from infection . and make unfavorable condition for bacterial growth  

(2) Acquired immunity -  acquired immunity is a resistance develop for specific antigen or resistance acquired by an individual during life time. individual adapt immunity by infection or vaccination by transfer  of antibody from an immune donor. acquired immunity commonly divided into the two types active and passive immunity.

• active immunity 
• passive immunity    

• active immunity - immunity resulting from the development of antibodies in the from of vaccination or exposed to an infection disease. active immunity means any antigen or foreign particle enter in body and body produced antibody against antigen that is active or adaptive immunity they are two types of active immunity 

    (A) natural   acquired active immunity
    (B) artificial  acquired active immunity

(A) natural acquired active immunity -  this immunity acquired by infection such as viral infection or bacterial infection it is acquired after an infection or recovery from disease . antibody produced response to infection in some cases immunity may be life long example measles small pox.

(B) artificial acquired active immunity - it may be acquired by artificially or archived by vaccination or toxic  which is preparation  of live attenuated or killed microorganism or pathogen or their antigen. artificial immunity get by individual through vaccination such as BCG ,TT, DT etc.

•   passive immunity  - the passive immunity is a readymade immunity. passive immunity transfer readymade antibody . the resistance transfer to the recipient in a ready-made from is called passive immunity example maternal antibodies are transfer to the fetus through the placenta passive immunity divided into the two type they are following -

(A)  natural  acquired passive immunity
(B)  artificial  acquired passive  immunity

(A)  natural  acquired passive immunity - the resistance transfer passively from mother to fetus through the placenta . immunoglobulin   IgG can transfer or cross the placenta. after birth antibodies are transfer to newborn baby through the breast milk.this is immunity made up under natural condition is called natural but recipient does not synthesize antibodies but get from donor that is passive.

(B) artificial  acquired passive  immunity - it is resistance transfer to a recipient by administration of antibodies. it is archived by toxic or vaccination.

Importance Of Immunity 

• immunity is the protection power of human body. 
• immunity protect from invasion of pathogen. 
• immunity is the natural defense system of human body. 
• immunity help to protection from microorganism.

Summary Of Immunity - 

the study of immunity help to understand immune power of the body and its function. immunity is the protection power of body its protect from invasion of pathogen it is resistances power of body. immunity mostly divided into two type natural and artificial. the natural immunity is the birth immunity it is transfer from one generation to other generation, natural immunity made before birth natural immunity is also individual immunity its come from birth. natural immunity divided into to types specific and non specific. the specific immunity generated in individual to any infection such as small pox and non specific immunity of individual such as skin,mucus,digestive system,urinary system,respiratory system etc they are help to protection from infection.artificial immunity it is ready made immunity its acquired after birth such as antibody transfer through mother milk and other example is vaccination or immunization. 

Mode of Transmission of Diseases

• The traditional epidemiologic triad model holds that infectious diseases result from the interaction of agent, host, and environment.
• More specifically, transmission occurs when the agent leaves its reservoir or host through a portal of exit, is conveyed by some mode of transmission, and enters through an appropriate portal of entry to infect a susceptible host. 
• An infectious agent may be transmitted from its natural reservoir to a susceptible host in different ways.
• There are different classifications for modes of transmission. 
• Diseases can be transmitted directly or indirectly.

Candida

• Normal Habitat: 
• mucosal membranes of human and other warm blooded animals.
• Also found in the gut, the vagina or also in the surface of the skin.
• Found in the digestive tract of birds also.
• Isolated from soil, animal, hospitals, in-animate objects and food.
• Worldwide distribution

• MORPHOLOGY
  
• Small, oval, measuring 2-4 µm in diameter.
• Yeast form, unicellular, reproduce by budding.
• Single budding of the cells may be seen.
• Both yeast and pseudo-hyphae are gram positive.
• Encapsulated and diploid, also form true hyphae.
• Polymorphic fungus (yeast and pseudohyphal form)
• Can form biofilms
• Normal condition: Yeast
• Special condition (pH, Temperature): Pseudohyphae
• 80-90% of cell wall is carbohydrate

• on SDA
• Creamy, pasty colonies, smooth after 24-48 hours at 25-37°C
• Yeast smell (odour)

Blood Agar

Candida albicans on Blood Agar

• White creamy colored
• Foot-like extensions from the margin.

• Opportunistic fungal pathogen that causes candidiasis in human
• Occurs in immunocompromised peoples such as HIV infected, transplant recipients, chemotherapy patients, etc.
• Mode of transmission:
• Mother to infant through childbirth
• Rarely through sexual contact
• People to people transmission in hospital settings

Stages of Infection

1. Colonization

• Epithelial adhesion
• Nutrient acquisition

2. Superficial Infection

• Epithelial penetration
• Degradation of host protein

3. Deep-Seated Infection

• Tissue penetration
• Vascular invasion
• Immune evasion or escape

4. Disseminated Infection

• Endothelial adhesion
• Infection of other host tissues
• Activation of coagulation and blood clotting cascades.

Types of Candidiasis

Mucosal Candidiasis

• Oral candidiasis: mucous membrane of mouth
• Denture related stomatitis: mild inflammation and redness of oral mucous membrane beneath a denture.
• Angular cheilitis: inflammation of one or both corners of the mouth
• Median rhomboid glossitis: redness and loss of lingual papillae
• Vulvovaginitis: white lesions on the epithelial surfaces of vulva, vagina and cervix
• Balanitis: infection of glans penis
• Esophageal candidiasis: infection of esophagus painful swallowing.

Cutaneous Candidiasis

• Candida folliculitis: infection and inflammation of hair follicles, rash may appear as pimples.
• Candidal intertrigo: infection of skin located between intertriginous folds of adjacent skin.
• Candidal paronychia: inflammation of the nail fold.
• Perianal candidiasis: irritation of the skin at the exit of the rectum.
• Chronic mucocutaneous candidiasis: immune disorder of T cells, deficient of CMI.
• Congenital cutaneous candidiasis: skin condition in new borne babies caused by premature rupture of membranes together with a birth canal infected with C. albicans.
• Diaper candidiasis: infection of a child’s diaper area.
• Erosio interdigitalis blastomycetia: characterized by an oval shaped area of macerated white skin on the web between and extending onto the sides of the fingers.
• Candidal onychomycosis: nail infection

Systemic Candidiasis

• Candidemia: leads of sepsis
• Disseminated candidiasis (organs)
• Endocarditis
• Gastro intestinal tract infection
• Respiratory tract infection
• Genitourinary candidiasis
• Hepatosplenic candidiasis (Chronic Disseminated Candidiasis)

Lab Diagnosis of Candida albicans

Specimens: Exudates, Tissues, Scrapings

1. Microscopy (Scraping)

• Examined in wet film in 10% KOH
• Visualization of pseudohyphae and budding yeast cells of candida
• Gram staining: Gram positive (+ve)

2. Culture

• SDA: Creamy white, smooth colonies
• CHROMAGAR: Green colonies

3. Identification of albicans

• Germ Tube Test: produce germ tube test within 2 hours when incubated in human serum at 37°C.
• Chlamydospores: produced by C. albicans on corn meal/rice agar at 25°C. They produces round thick walled chlamydospores borne terminally or laterally.
• Biochemical Tests: Glucose and maltose fermented with acid and gas production, sucrose and lactose not fermented, Pale pink coloration in Tetrazolium reduction medium

4. Serology

• Limited specificity
• Serum antibodies and cell mediated immunity are demonstrable in most people because of life long exposure to C. albicans.
• C. albicans antigen is a delayed hypersensitivity skin test, which is used as an indicator of functions of the CMI.
• ELISA and RIA: detection of circulating Candidial antigen either cell wall mannan or cytoplasmic constituents.

5. 1,3-beta-D-glucan assay

• Beta-D-glucan is a component of the cell wall of fungi.
• Detected by its ability to activate factor G of the horse-shoe crab coagulation cascade.
• Highly specific and sensitive test.

6. DNA probe and PCR

Treatments of Candida albicans

1. Oral candidiasis: Nystatin, miconazole, amphotericin B.
2. Cutaneous candidiasis: Clotrimazole, econazole, ciclopirox, miconazole, ketoconazole, nystatin.
3. Systemic and oral azoles: Fluconazole, itraconazole or posaconazole.
4. Vulvovaginitis: single dose of oral fluconazole, topical antifungals (butoconazole, clotrimazole, miconazole, nystatin, ticonazole, terconazole).
5. Blood infections: intravenous fluconazole or an echinocandin (caspofungin)
6. Candidemia: Fluconazole and Anidulafungin