Question

what is vaccination?write its mechanism?

Answer 1

Vaccination. Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a pathogen. Vaccines can prevent or ameliorate infectious disease.

Answer 2

A vaccine is a biological preparation that provides active acquired immunity to a particular disease.The invention of vaccination was a turning point in the war between microbes and humans. Although improved sanitation and antibiotics may have saved more lives, vaccines represent the most cost-effective life-saving device in history. Despite their success, one of the great iro-nies of vaccinology is that the vast majority of vaccines have been developed empirically, with little or no understanding of the immunological mechanisms by which they induce protective immunity. However, the failure to develop vaccines against global pandemics such as infection with human immunodeficiency virus (HIV) despite decades of effort has underscored the need to understand the immunological mechanisms by which vaccines confer protective immunity. It is now clear that the immune system has evolved qualitatively different types of responses to protect against different pathogens. For example, distinct subsets of helper T cells, such as TH1, TH2 and TH17, are effective at protecting against different pathogens1 (Table 1). Follicular helper T cells (TFH cells) produce interleukin 21 (IL-21) and help with the differentiation of B cells and generation of memory B cells2. In addition, differentiating memory CD4+ and CD8+ T cells can be subcategorized into central memory and effector memory cell subsets, each with a distinct functionality3. This places a great premium on understanding and harnessing the mechanisms that stimulate such diverse responses in the context of vaccines against different pathogens. Research during the past decade has identified a fundamental role for the innate immune system in sensing vaccines and adjuvants and in programming protective immune responses. The innate immune system can sense microbes through pattern-recognition receptors (PRRs), such as the Toll-like receptors (TLRs), which are expressed by various cells, including dendritic cells (DCs)4,5. In addition to TLRs, other types of PRRs, including the C-type lectin-like receptors6 and the cytosolic Nod-like receptors7, sense a broad range of microbial stimuli, and the cytosolic RIG-I-like receptors sense viral nucleic acids8. There are many subsets of functionally distinct DCs, and it is now clear that the DC subset, as well as the nature of the PRR, have a key role in determining the magnitude and quality of adaptive immune responses9,10.