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histoplasmin 329 HIV-1 genes
G-O HLA-DP HLA-DQ HLA-DR C4 BF C2 TNF HLA-B HLA-C
HLA-A
5¢ 3¢
B2
mediated response in humans occurs in lymphoid organs and
other tissues 7 to 18 days following exposure to conidia. This
leads to initiation of the healing of lesions and organs with
the formation of granulomas having central necrosis. Lymph
nodes that drain sites of infection are large and encapsulate
and may calcify. Delayed-type hypersensitivity responses
to histoplasmin are detectable a month after infection.
Macrophages and neutrophils may harbor H. capsulatum.
Yeasts and conidia that are not coated with opsonins bind
to epitopes of the lymphocyte-function-associated antigen 1
(CD11a/CD18), complement receptor type III (CD11b/CD18),
and the P-150–195 complex (CD11c/CD18) of adhesionpromoting
receptors on human macrophages. Yeast binding
requires divalent cations. Human macrophages form hydrogen
peroxide. Histoplasma yeasts fail to induce a respiratory burst
when phagocytosed. Antigen-specific CD4 + T lymphocytes
mediate both protective immunity and delayed-type hypersensitivity.
Cytokines that influence the outcome of infection in
naïve animals include interleukin 12 (IL12) and tumor necrosis
factor α (TNF-α). IL3, granulocyte–macrophage colonystimulating
factor (GM-CSF), and macrophage CSF activate
human macrophages to block yeast cell growth. There is no
licensed vaccine for H. capsulatum, but its heat shock protein
system may be a promising candidate for a future vaccine.
histoplasmin
An extract from cultures of Histoplasma capsulatum that is
injected intradermally, in the same manner as the tuberculin
test, to evaluate whether an individual has cell-mediated
immunity against this microorganism.
histoplasmin test
A skin test analogous to the tuberculin skin test, which determines
whether an individual manifests delayed-type hypersensitivity
(cell-mediated) immunity to Histoplasma capsulatum,
K2 K
A b3
A2 B1 A1 B2 A2
Class I
I-A I-E
Ab2 Ab Aa Eb Eb2 21-
OHB
C4
21-
OHA
E a
Slp
B1
the causative agent of histoplasmosis in humans. A positive skin
test implies a current or earlier infection with H. capsulatum.
histotope
That portion of a major histocompatibility complex (MHC)
class II molecule that reacts with a T lymphocyte receptor.
Hitchens, A. Parker
First chairman of the American Association of
Immunologists Council, father of the association’s constitution
and bylaws and the force behind development of an
association journal.
HIV
Abbreviation for human immunodeficiency virus.
HIV-1 genes
The gag gene encodes the structural core proteins p17,
p24, p15, and p55 precursor. The pol gene encodes a protease
that cleaves gag precursors. It also encodes reverse
transcriptase, which produces proviral DNA from RNA,
and an integrase necessary for proviral insertion. The env
gene encodes gp160 precursor, gp120, and gp41 in mature
proteins; gp120 binds CD4 molecules; and gp41 is needed
for fusion of the virus with the cell; the function of vpr is
unknown; vif encodes a 23-kDa product that is necessary
for infection of cells by free virus and is not needed for
infection from cell to cell; tat encodes a p14 product that
binds to viral long terminal repeat (LTR) sequence and activates
viral gene transcription; rev encodes a 20-kDa protein
product required for post-transcriptional expression of gag
and env genes; nef encodes a 27-kDa protein that inhibits
human immunodeficiency virus (HIV) transcription and
slows viral replication; and vpu encodes a 16-kDa protein
product that may be required for assembly and packaging of
new virus particles.
Class II
Bf
A1
TNF TNF D D2 D3 D4 L
C2
Q1
B1
Short arm of human chromosome 6.
Class III
Q2
B2
Class I
H-2 complex on chromosome 17 of a mouse.
Q4
B5
Q5
B3
Q6
B4
A
Q7 Q8/9 Q10
H