Adjuvant - a substance that when mixed with, or administered simultaneously with an antigen, increases the immunological response to that antigen.

Anamnestic response - the immune response to an antigen that is dependent on the administration of the antigen to which the subject had previously developed a primary immune response; also called memory response, booster response, recall response, second set response, and secondary immune response. Anamnestic responses produce antibody or activated cells more rapidly and to a greater extent than in primary immune responses.

Antibody - an immunoglobulin molecule that contains antigen binding sites to bind specifically to an antigenic determinant. Antibodies may block or neutralize pathogen adherence to target cells, activate complement systems, opsonize particulate antigens or specifically direct killer cells. Antibodies are large glycoproteins produced by differentiated B lymphocytes (plasma cells) in response to antigenic stimulation. There are several isotypes and sub-isotypes of antibodies such as IgA, IgE, IgD, IgG and IgM. Antibodies are found in high concentration in plasma (10% of the total protein mass) and to a lesser degree in almost all body fluids.

Antibody Dependent Enhancement (ADE) - enhanced, accelerated or more severe disease in vaccinated cats after viral challenge as a result of pre-existing virus neutralizing antibody. The concentration of antibody is critical for enhancement of infection, in the case of FIP, of peritoneal macrophages.

Antigen - any substance which is capable, under appropriate conditions, of inducing an immune response that reacts specifically in some detectable manner with the antibodies or cells so induced. Antigens may be soluble substances, such as toxins and foreign proteins, or particulate, such as bacteria and tissue cells.

Biologicals - medicinal preparations made from living organisms and their products, including serums, vaccines, antigens, antitoxins, etc.

Booster dose - Repeated administration of vaccine at some time after the initial administration in order to enhance or "boost" the level of immunity and/or to increase immunologic memory.

Cell-mediated immunity (CMI) - specific acquired immunity in which the role of small T lymphocytes (of thymic origin) is predominant in the effector mechanisms; it is responsible for resistance to infectious diseases caused by certain bacteria and by viruses, certain aspects of resistance to cancer, delayed hypersensitivity reactions, certain autoimmune diseases and allograft rejection, and plays a role in certain allergies.

Duration of Immunity (DOI) - the length of time from vaccination or infection that an immune response is protective against experimental challenge or in the field against natural challenge.

Efficacy - the measurement of effectiveness of a vaccine.

Epizootic - a disease of high morbidity which is only occasionally present in a population.

Exogenous - originating outside of an organism.

Humoral immunity - acquired immunity in which the role of circulating antibodies (immunoglobulins) is predominant in the effector mechanisms.

Immunity -1. the condition of being immune; security against a particular disease; nonsusceptibility to the invasive or pathogenic effects of foreign microorganisms or to the toxic effect of antigenic substances.

Immunization - the process of rendering a subject immune, or of becoming immune. Active immunization - inoculation with a specific antigen to induce an immune response. Passive immunization - the conferral of specific immune reactivity on previously nonimmune individuals by the administration of sensitized lymphoid cells or serum from immune individuals.

Immunocompetence - the ability or capacity to develop an immune response (i.e. antibody production and/or cell-mediated immunity) following antigenic challenge; also called immunologic competence.

Immunocompromised - a deficiency in immune response, either in that mediated by humoral antibody or in that mediated by immune T-lymphoid cells or a combined immunodeficiency; the state of less than ideal immunocompetence.

Infection -1. invasion and multiplication of microorganisms in body tissues, resulting in local cellular injury due to competitive metabolism, toxins, intracellular replication, or antigen-antibody response. The immunological response may be transient or prolonged, and consists of a cellular response or the production of specific (immunoglobulin) antibody to the components of the infecting organism or its toxins.

Infectious - infective; capable of producing infection; pertaining to or characterized by the presence of pathogens

Informed consent (or declination) - a client's agreement to allow a procedure based on a full disclosure of all of the known facts (benefits, risks, and alternatives) necessary to make an intelligent decision.

Licensure - the processes of application for a USDA license to produce and sell a biological product that assures purity, potency, safety and efficacy.

Maternal antibodies - antibodies, (e.g. predominantly of the IgG class) produced in the body of the mother and transferred to the fetal circulation and to the neonate via colostrum.

Monovalent vaccine: denoting an antibody capable of combining with only one antigenic specificity or an antigen capable of combining with only one antibody specificity; more commonly used to designate a vaccine against a single infectious disease.

Multivalent vaccine: a vaccine containing more than one antigen which may be from different organisms or different strains of the same organism.

Panleukopenia virus/feline enteritis virus/feline parvovirus (FPV) -interchangeable terms for a virus etiologically responsible for disease characterized by destruction of rapidly dividing cells in the gastrointestinal tract and bone marrow of cats that is usually fatal in kittens.

Parenteral - by a route not through the alimentary canal.

Serological titers - The reciprocal of the highest dilution of serum or other fluid that contains immunoglobulin that will produce an observable or measurable effect (antibody activity) against a given antigenic preparation.

Specific pathogen free (SPF) - an unvaccinated animal raised and maintained in a barrier or isolation facility, that is free of all known pathogens, or at least free of a known set of pathogens.

Univalent vaccine: see monovalent vaccine

USDA - United States Department of Agriculture; the federal agency responsible for the approval and licensing and regulation of animal biologicals. It exercises its regulatory authority through APHIS (Animal, Plant Health Inspection Service).

Vaccination - the administration of vaccine for the purpose of inducing immunity.

Vaccine, avirulent live - similar to modified live, but applies to a vaccine made from organisms that are nonpathogenic, but which are immunogenic.

Vaccine, killed - a vaccine made from an organism that has been rendered incapable of infection or replication but retains immunogenicity.

Vaccine, live vector - a vaccine made from an avirulent viral or bacterial vector that carries and expresses a genetic construct that encodes for antigenic determinants of an unrelated infectious agents for the purpose of stimulating active immunity to the infectious agent.

Vaccine, modified live - a vaccine made from a virus that through laboratory based manipulation has been altered to make it avirulent for the specified recipient. The MLV vaccine is still infectious and immunogenic.

Vaccine, subunit - a vaccine made from a subset of antigens critical in stimulating a protective immune response against the full array of antigens that would be found in complementary whole organism vaccine or culture. Subunit vaccines may be a synthetic molecule that has the same physical structure and chemical composition as antigenic determinants of the whole antigen. The subunits may be covalently bound to carrier molecules and mixed with adjuvants or other immunostimulants.

Viral challenge - administration of a dose of live, virulent virus to evoke disease in susceptible animals. Challenge studies are used to test the efficacy of vaccines by determining if the animal has protective immunity

Virulence - the degree of pathogenicity of a microorganism as indicated by the extent of morbidity and/or mortality , tissue destruction and tissue invasion.

Virus neutralizing (VN) antibody titers - The reciprocal of the highest dilution of the quantity of antibody present in serum or other fluid that is capable of neutralizing the biological activity of a virus by blocking adherence or replication of a virus in cell culture or in vivo.