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sex hormones and immunity 649 Sézary cell
Severe combined immunodeficiency (SCID) syndrome.
Maturation of T and B lymphocytes.
Even attenuated microorganisms such as those used for
immunization (e.g., attenuated poliomyelitis viruses) may
induce infection in SCID patients. Graft-vs.-host disease is
a problem in patients receiving unirradiated blood transfusions.
Maternal–fetal transfusions during gestation or at
parturition or blood transfusions at later dates provide sufficient
immunologically competent cells entering the SCID
patient’s circulation to induce graft-vs.-host disease. SCID
may be manifested in one of several forms; it is classified as
a defect in adenosine deaminase (ADA) and purine nucleoside
phosphorylase (PNP) enzymes and in a DNA-binding
protein needed for human leukocyte antigen (HLA) gene
expression. Treatment is by bone marrow transplantation
or gene therapy and enzyme reconstitution in cases caused
by a missing gene such as ADA deficiency. X-linked SCID
(XSCID), induced by defects in IL2RG, the gene encoding
the interleukin-2 (IL2) receptor γ chain, is the major genetic
form. It occurs in 1 in 50,000 to 100,000 births. Only
males, who have single X chromosomes, become ill with
XSCID. Females may be carriers, passing along the condition
to male offspring. A previously fatal disease, XSCID
is now effectively treated by bone marrow transplantation.
The cause and pathogenesis of the disease are known and
specific gene defects can be identified and traced in patients
and at-risk family members.
sex hormones and immunity
Females are more susceptible to certain autoimmune
diseases than males, an observation that immediately led
to suspicion that sex hormones played a role. The exact
mechanisms through which sex steroids interact with the
immune system remain to be determined, but sex hormones
exert direct effects on immune system cells and indirect
effects through cells that control growth and development
of the immune system or through organs that are ultimately
destroyed by autoimmune reactions. Female mice synthesize
more antibodies in response to certain antigens than
males, but humans injected with vaccines show essentially
identical antibody responses regardless of sex. Murine
cell-mediated responses to selected antigens were stronger
in females than in males. Sex steroids have profound effects
on the thymus. Androgen or estrogen administration to
experimental animals led to thymic involution and castration
led to thymic enlargement. The thymus is markedly
involuted during pregnancy, but achieves its normal size
and shape following parturition. Sex steroids have numerous
targets including bone marrow and thymus where the
precursors of immunity originate and differentiate. Further
studies determined how sex hormones control cytokine
genes. Sex steroid hormones affect the development and
functions of various immune system cells.
sex limited protein
Refer to slp.
Sézary cell
T lymphocytes that form E rosettes with sheep red cells
and react with anti-T antibodies. Sézary cells from most
individuals show diminished responses to plant mitogens,
although those from a few demonstrate normal reactivity.
Sézary cells are also poor mediators of T cell cytotoxicity,
but they can produce a migration inhibitory factor (MIF)like
lymphokine. Sézary cells do not produce immunoglobulin
or act as suppressors. They exert helper effects for
immunoglobulin synthesis by B cells.
Lymphocyte from a patient with Sézary syndrome.
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