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Paratope
An antibody combining site that is complementary to an epitope.
Passive immunization
Immunization by the administration of preformed antibody into a nonimmune individual.
Phagocytosis
The engulfment of a particle or a microorganism by leukocytes.
Phenotype
The physical expression of an individual's genotype.
Pinocytosis
Ingestion of liquid or very small particles by vesicle formation in a cell.
Plasma cell
End-stage differentiation of a B cell to an antibody-producing cell.
Polyclonal activator
A substance that induces activation of many individual clones of either T or B cells. See Mitogen.
Polymorphism
Literally, "having many shapes"; in genetics polymorphism means occurring in more than one form within a species; the existence of multiple alleles at a particular genetic locus.
Polymorphonuclear leukocyte
White cell, granular cytoplasm. Neutral staining (neutrophil) - most frequent, phagocytic. Basophilic staining - basophil q.v. Eosinophilic staining - eosinophil q.v.
Primary lymphoid organs
Organs in which the maturation of T and B lymphocytes take place and antigen-specific receptors are first acquired.
Primary responses
The immune response to a first encounter with antigen. The primary response is generally small, has a long induction phase or lag period, consists primarily of IgM antibodies, and generates immunologic memory.
Prophylaxis
Protection.
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