eChapters

Today, organic and local foods are preferred as they use less pesticides or fertilizers. However, these foods, like others, can be exposed to harmful bacteria during the growing and harvesting process. The farmers and distributors must use good sanitary practices to minimize food contamination. Consumers should cook food properly. The street food vendors are a traditional and indigenous fast food approaching in most countries of the South-East Asia Region. As these are economical they cater to millions of consumers. Among safe street foods there are many contributing factors that are associated with the safety of street food. WHO had conducted a survey in 1993 covering 100 street foods in 100 countries around the world. It revealed that the major health threat comes from raw and undercooked food, infected food handlers and inadequate hygiene practices in processing and storing such food. If the street food is cooked well and is served hot, then the chances of food poisoning is less. The water quality, hygienic conditions and the level of cleanliness especially in the summer season are the major factors for food poisoning. However improvements in physical infrastructure and hygienic conditions are growing as consumers are also demanding quality food. Michael et al., (2017) have looked into organic versus conventional foods.

Humoral immune response is the immune response which is mediated by antibodies.. It is called humoral immune response because antibodies are transferred with the ‘humour’ that is fluid or blood. Antibodies are the proteins produced by B lymphocytes.

The immune system protects the body from harmful substances by recognizing and responding to antigens. Antigens are the protein molecules which are present on bacteria, virus, fungi or some other microorganisms.Some toxins can also be antigens. These antigens are recognized by immune system. The destruction of antigens by producing antibody is called antibody-mediated immune response. As antibodies are present in the body fluids i.e. humors,this type of response is called humoral immune response.

This chapter introduces hybridoma technology and its application in producing monoclonal antibodies. It explains the fusion of antibody-producing B lymphocytes with immortal myeloma cells, selection in HAT medium and the roles of HGPRT and polyethylene glycol. The survival and cloning of hybrid cells and the advantages of monoclonal antibodies are considered. The chapter also discusses tissue and organ transplantation, including autografts, isografts, allografts and xenografts. The immunological mechanisms of acute graft rejection, donor histocompatibility antigens and the involvement of T lymphocytes are addressed. These questions connect laboratory antibody production with transplantation immunology and its diagnostic, therapeutic and research applications.

This chapter explores the four types of hypersensitivity reactions described under the Gell and Coombs classification. Type I immediate hypersensitivity, Type II cytotoxic reactions, Type III immune-complex disease and Type IV delayed hypersensitivity are examined in detail. The roles of IgE, mast cells, basophils, antibodies, complement and T lymphocytes are highlighted. Clinical examples include anaphylaxis, milk allergy, haemolytic disease, transfusion reactions, serum sickness, glomerulonephritis, farmer’s lung and the blue-eye condition associated with canine hepatitis. Diagnostic applications, including the tuberculin and Coombs tests, are also addressed. The chapter explains how exaggerated or inappropriate immune responses can damage tissues and produce disease.

The basic purpose of the immune system is to provide defense to the body from various types of infections. But, sometimes, the system which is aimed to provide protection become damaging or even life-threatening. There are situations when immune response against harmless and inert antigens is exaggerated and cause diseases.

The immune system has been designed to provide protection to the body from various diseases. But the same system which is aimed to provide protection may sometimes become harmful to the body and may even life-threatening. There are situations when immune response against harmless and inert antigens is exaggerated and actually causes diseases. Such a condition is called hypersensitivity or commonly as allergy. Though the term ‘hypersensitivity’ indicates an increased response but the immune response is not always heightened, instead it may be an inappropriate response to an antigen.

Mange or parasitic dermatitis is caused by the infestation of mange mites e.g. Sarcoptes, Psoroptes, Demodex spp. and a range of other mites. The condition is characterized by itching and rubbing of the infested parts of the body against hard objects. Lesions include hair loss, dry, rough, thickened and wrinkled skin accompanied by the presence of scab and foul odour in some cases. Some mites burrow into the host epidermis (Sarcoptes) while others spend their entire life cycle on the skin surface (Psoroptes). Most mites are microscopic or less than 1mm in length; therefore skin scrapings are taken from the affected area of animals suspected to be suffering from mange or parasitic dermatitis

Infectious diseases are the result of a complex interaction between the host and the microbes. Evasions of protective immunity by the parasites critically determine the survival and pathogenicity of the microbes. The invasion of the body by harmful microorganisms is called infection.

Infection refers to the invasion of harmful microorganisms into the body and causing disease. The most important function of the immune system is to protect the body of the host against various viruses, bacteria, fungi and parasites. The grounds of immune surveillance stand on the basis of innate and specific immunity that build up against the evasive mechanisms of the disease causing organisms. Infectious disease is result of a complex interaction between  the host and the microbes. Evasions of protective immunity by the parasites critically determine the survival and pathogenicity of the microbes. The invasion of the body by harmful microorganisms is called infection. Infections are dangerous in any part of the body. Microorganisms spread vary easily into the blood stream and cause blood poisoning which is called septicemia.

A. Answer the following.

Q.1.     How lysozyme kills Gram + and Gram – bacteria ?
Ans.     Lysozyme kills Gram + bacteria by splitting cell wall proteoglycans and Gram – bacteria in conjunction with complement.

Q.2.     Describe the different forms of leprosy ?
Ans.     Leprosy occurs in two different forms (1) tuberculoid (2) lepromatous. Tuberculoid leprosy occurs in 80% cases. Tuberculoid leprosy patients mount a strong CMI response. These patients have few organisms in their tissues and therefore few lesions. The lesions are infiltrated with macrophages and patients show a positive delayed type hypersensitivity reaction to I/D

The study of the immune system, in its various aspects, is called immunology. Immunology is the branch of bioscience which deals with the defense mechanisms including all physical, chemical and biological properties of the organism that help it to combat its susceptibility to foreign agents and microorganisms. Immunology includes the development and functions of various components of immune system by which the body responds, destroys or neutralizes foreign agents or pathogens. It includes the study at cellular as well as molecular level. Immunology is an interdisciplinary subject which incorporates and requires the knowledge of many branches of biology like microbiology, biochemistry, molecular biology and clinical medicine.

In animals with a long gestation period, such as domestic animals, the acquired immune system is fully developed at birth, but cannot function at full adult levels for several weeks. The complete development of the acquired immunity depends on antigenic stimulation. The proper development of B cells and B cell antigen receptor (BCR) diversity requires clonal selection and antigen driven cell multiplication. Thus, the newborn animals are vulnerable to infection for the first few weeks of life. Hence, the temporary assistance in defending themselves at this time is provided by the mother in the form of antibodies and possibly T cells.
 
Development of the Immune System

The thymus is first lymphoid organ to develop, followed closely by the secondary lymphoid organs. B cells appear soon after the development of spleen and  lymph nodes, but antibodies are not usually found until late in foetal life, if at all. The ability of fetus to respond to antigens develops very rapidly after the lymphoid organs appear, but all antigens are not equally capable of stimulating fetal lymphoid tissue. The immune system in a series of steps, each step permitting the foetus to respond to more antigens. These steps are driven by a gradual increase in the use of gene conversion or somatic mutation to antibody diversity. The ability to mount cell mediated immune (CMI) responses develops at the time as antibody production. Data from humans suggest that T cell receptor diversity is limited in the fetus and neonate and that cytokine production may be low. This may simply be due to their lack of to foreign antigens.

Diagnosis of parasitic infections is routinely done with conventional parasitological techniques as described earlier. However, when the parasitaemia is too low to be detected by the conventional methods as in subclinical infections and/or carrier animals advanced diagnostic tools are used for the early, sensitive as well as specific diagnosis. Serological techniques Diagnostic techniques used mostly in laboratories needs various reagents and equipments to perform the test. However, a diagnostic kit is the extrapolation of the same method by packing it in a user friendly format, accompanied by all or most of the reagents required to perform the test and can also be done outside the lab or under field conditions. Various immunodiagnostic kits are available which are based on different diagnostic methods like Enzyme-linked immuno sorbent assay (ELISA). Complement fixation test (CFT), Agar gel immunodiffusion test (AGID), Immunofluorescent tests (IFT), Latex agglutination tests (LAT) etc. ELISA is the most commonly used test system and numerous kits based on ELISA are available commercially.

The wellbeing of a person depends on his immune system. Any deficiency in any component of the immune system is called immunodeficiency and it may impair the normal functioning of his body and makes the person more susceptible to infections.

The well-being of a person depends on his immune system. Any deficiency in any component of immune system may lead to defects in the normal functioning of his body and makes him more susceptible to diseases. The immunodeficiency may be either in specific components (B cells or T cells) or nonspecific component (phagocytes and complement) of the immune system.

A. Answer the following.

Q.1.    Which protein is coded by gag gene in HIV ?
Ans.     It codes for protein that form the core (p24 and p17).

Q.2.     Which protein is coded by pol gene in HIV ?
Ans.    It codes for a protein that cleaved into 4 enzymes. 

Q.3.     Which protein is coded by env gene in HIV ?
Ans.    It codes for protein that is cleaved into two proteins (gp120 and gp41).

This chapter focuses on the structure, classes, properties and biological functions of immunoglobulins. It introduces the basic antibody molecule, including heavy and light chains, variable and constant regions, antigen-binding sites and Fc fragments. The characteristics of IgG, IgM, IgA, IgE and IgD are examined in relation to their distribution and immune functions. Questions cover primary and secondary immune responses, placental transfer, mucosal protection, allergic reactions, complement activation and agglutination. The chapter also addresses antibody affinity, avidity, isotypes, allotypes, idiotypes, class switching and Bence-Jones proteins. It provides essential knowledge of how antibodies recognize antigens and contribute to immune protection and diagnosis.

Immunological Causes of Male Infertility

Immune mediated male infertility is an auto-immune disease.Spermatozoa are first produced at puberty and isolated from the systemic circulation by a structural barrier maintained by Sertoli cell tight junctions within the testis and the uninterrupted epithelial cell lining of the excurrent ductal system. Sperm production occurs well after the development of immunological tolerance to self antigens; therefore sperm specific components are viewed as foreign by the immune system. Whether spermatogonia, the primordial cell in spermatozoa differentiation, is also antigenically foreign is not established. What is known , is that immunization with sperm elicits a highly reproducible immune response that can impair fertility.

Antisperm antibodies are found in about 10-15% of infertile men. Immunity only to those antigens present on the surface of viable, motile sperm will impair fertility. Antibodies to internal sperm antigens, due to an immune response to sperm degraded in the genital tract or to cross reacting microbial antibodies present in the sera of many fertile individuals , are of questionable relevance to infertility. A number of spermatozoa antigens have been identified .

The pathogenicity of an organism varies form mild attack to severe fatal attacks. The host has many mechanisms to resist or to avoid the pathogens apart from immune systems. One or few of these will be activated when the pathogen enters into the body. Following are some of the listed natural host defense mechanisms.