Glossary

Term	Definition	NEET Context
Retrovirus	Virus with RNA genome that uses reverse transcriptase to convert RNA to DNA	HIV is a retrovirus; reverse transcriptase is key enzyme
CD4+ T-helper cells	T-lymphocytes bearing CD4 surface marker; coordinate adaptive immunity	Primary target of HIV; loss leads to AIDS
Reverse transcriptase	RNA-dependent DNA polymerase in retroviruses; converts viral RNA to DNA	Carried by HIV; target of NRTI antiretrovirals
Haemozoin	Insoluble ferriprotoporphyrin IX crystal formed by Plasmodium from digested haemoglobin	Causes fever when released upon RBC lysis in malaria
Schizogony	Asexual multiple fission in Plasmodium	Liver schizogony (exo-erythrocytic) + RBC schizogony (erythrocytic)
Gametocyte	Sexual stage of Plasmodium; taken up by female Anopheles mosquito	Male + female gametocytes → fertilization in mosquito
Hypnozoite	Dormant liver form of P. vivax/P. ovale causing relapse	Eliminated by primaquine; absent in P. falciparum
Metastasis	Spread of malignant cancer cells to distant sites via blood/lymph	Defines malignancy; benign tumors do NOT metastasize
Oncogene	Mutated proto-oncogene that promotes uncontrolled cell division	ras, myc, bcr-abl; gain-of-function mutations
Tumor suppressor	Gene that inhibits cell division; loss leads to cancer	p53, Rb; loss-of-function mutations in cancer
Phagocytosis	Engulfment of pathogens by macrophages and neutrophils	Key function of cellular barriers in innate immunity
Plasma cell	Terminally differentiated B-cell that secretes antibodies at high rate	Effector cell of humoral immunity; secretes 1000-2000 Ig/second
Interferons	Cytokine proteins produced by virus-infected cells to warn neighbors	Part of cytokine barrier; IFN-α, IFN-β (viral), IFN-γ (immune)
Widal test	Agglutination test detecting antibodies against Salmonella typhi O and H antigens	Standard serological diagnosis of typhoid fever
ELISA	Enzyme-Linked Immunosorbent Assay; detects antibodies or antigens	Standard HIV screening test; also used for other infections
Elephantiasis	Massive lymphoedema caused by Wuchereria bancrofti blocking lymphatic vessels	Transmitted by Culex mosquito
Colostrum	First breast milk; rich in secretory IgA	Provides passive immunity to neonate's mucosa
Autoimmunity	Immune response against self-antigens due to failure of self-tolerance	Rheumatoid arthritis (synovium), Type 1 DM (pancreas)
Active immunity	Immunity acquired through own antibody production (infection or vaccination)	Slow onset, long-lasting, memory cells formed
Passive immunity	Immunity acquired through preformed antibodies from external source	Immediate onset, short-lived, no memory cells
Dopamine transporter (DAT)	Membrane protein that removes dopamine from synapse via reuptake	Blocked by cocaine → excess dopamine → CNS stimulation
Diacetylmorphine	Chemical name for heroin; derived from morphine (Papaver somniferum)	Potent CNS depressant; mu-opioid receptor agonist