Microbiology Semester 2 Week 13

                Assalamualaikum and hi everyone... how are you all? I hope everyone will be fine as well... On Tuesday, before our class start, my classmates do their Pecha Kucha about a microbe based on topics provided to them.

                On Friday, Dr Asilah taught us about antigen and antibody. Antigens (Ag) is any agents capable of binding specifically to components of the immune response (e.g. antibodies). Immunogens is any agents capable of inducing an immune response. Requirements for immunogenicity is foreignness, high molecular weight (usually > 5000), chemical complexity and biodegradability. Major Classes of Antigens which is carbohydrates (polysaccharides) is potential (not always) immunogenic. Generally, ~ 6 sugar residues is recognized by antibody. Proteins is almost all are immunogenic. Generally, recognition by antibody is 15-22 amino acid residues. Lipids is rare (Often through conjugation with protein carriers). Nucleic acids is extremely poor (need conjugation with protein carriers). Contact points on the antigen for the immune system’s elements which is Epitopes / Antigenic determinants is the immunologically active portions of an antigen that reacts with antibodies or T-cell receptors. Epitopes can be sequential which is continuous and linear. Nonsequential is discontinuous, conformational and assembled topographic determinants. Types of responses generated is primary response (1st encounter) also known as the Priming Immunization. Antigen processing and lymphocytes proliferation and differentiation. Secondary response (2nd encounter) also known as the Memory or Anamnestic Response. Response quicker and the magnitude higher and mediated by B and T memory lymphocytes.

             Antibody (Ab) also called Immunoglobulins (Ig). Antibody (Ab) is a glycoprotein and also called Immunoglobulins (Ig). Depicted as a “Y” shaped structure consisting of 4 protein subunits which is 2 longer subunits is heavy (H) chain and identical and 2 shorter subunits light (L) chain, identical and two types (κ and λ chains). Recognition by antibody, antigens and epitopes. Antigen is molecules that antibody binds, can be proteins, polysaccharides (sugars), lipids or nucleic acids, can be located on the surface of the pathogen or excreted (toxin) by pathogen and the specific part of the Ag that the Ab binds is called the antigenic epitopes. Five classes of antibody which is IgM, IgG, IgE, IgD and IgA. Requirements for antibody production is only make Ab that are specific for antigens that one has been exposed to, make different classes of Ab with different functions and make high affinity antibody. High affinity antibody achieved by high affinity pre-existing B cells are clonally selected and select B cells with low affinity and increased affinity with development of Ab response which is affinity maturation. Differentiation into plasma or memory cells Plasma cells is majority, different lifespans (weeks to months) and secrete antibody. Memory cells is involved only those that have switched class. Memory cells for IgG, IgA and IgE not IgM or IgD. Retained Ig on their cell surfaces.