Differentiation stages of human natural killer cells in lymphoid tissues from fetal to adult life

Virtually all human granular lymphocytes expressed the HNK-1 differentiation antigen when examined in lymphoid compartments from adults, neonates, and fetuses. The HNK-1+ cells were distinguishable into three subsets having distinct antigenic phenotypes: HNK+T3-M1-, HNK+T3+M1-, and HNK+T3-M1+. Thus, greater than 70% of the HNK-1+ cells from 13-17 wk fetuses (less than 0.2% of nucleated cells) lacked T cell antigens (e.g., T3, T8, T4, and T6) and the M1 myeloid antigen. Morphologically, the HNK+T3-M1- cells consisted of three different types: small granular lymphocytes (less than 10% of HNK-1+ cells), agranular small lymphocytes with a narrow rim of cytoplasm (70-80%), and agranular giant cells (greater than 15 micrometers) with considerable neutrophilic cytoplasm (15%). The purified fetal HNK-1+ cells exhibited a low level of cytotoxicity against K562 target cells. On the other hand, almost all of HNK-1+ cells in neonatal tissues as well as adult bone marrow, lymph node, and thymus, exhibited the HNK+T3+M1- phenotype, contained sparse cytoplasmic granules, and had an intermediate level of NK functional activity. Only adult blood and spleen contained a majority of mature HNK-1+ cells. These cells had an HNK+T3-M1- phenotype, abundant cytoplasmic granules, and maximum NK function. We propose that human NK cells may generate from a separate cell lineage and that they alter their phenotype, morphology, and functional capability during differentiation.

[Oropharyngeal lymphoid tissue as a bursa-equivalent structure: embryological and clinical considerations]

If we examine with an ontogenetic viewpoint the tissues giving origin to both thymus and avian bursa of Fabricius, we can't ignore that they are primary lymphoid organs connected to areas of ecto-entodermic junctions. They have a strong development in the embryonic life while tending to regress in the adult. The analysis of the organogenesis clarifies this affirmation. In the human cephalic district we know of various ectoentodermic stratification areas: the branchial pockets and the Remake pharyngeal membrane. The oral-pharyngeal lymphoid tissue is histogenetically linked to the stem-cells of the marrow which migrate to occupy an initially ecto-entodermic milieu. Structural and ontogenetic analogies of embryological nature lead to an identification of the oral-pharyngeal lymphoid tissue in man with the avian bursa of Fabricius. Therefore we deem it very indicative that a humoral immunological deficiency syndrome appears in subjects with the atrophy of the Waldeyer ring; above all considering that an experimental model of the humoral immunological deficit has been reproduced in chicken surgically or hormonally bursectomized.

[Odontostomatogenic focal disease; embryologic and clinical causes of autoimmune pathogenesis]

The autoimmune pathogenesis of the focal odontostomatogenous disease is investigated and emphasis is laid on the different keys of interpretation: at embryologic, clinic and immunologic level. A special attention is paid to the primary meaning of structured or non structured lymphoid tissue of oropharynx, on account of embryologic identity with thymus and bursa of Fabricius, differentiating into sectors of ecto-entodermic stratification. The clinical evidence of the bursa-equivalent significance of Waldeyer ring, appears to lie in the ascertainment of the tonsillar atrophy in course of agammaglobulinaemia of Bruton type. The active chronic irritant phlogistic stimulus in a primary structure could excite the normal production of intolerant clones, so as to exceed the normal physiological homeostasis (giving rise to the autoimmune disease), or alter the mosiac self, inducing a production of autoantibodies.

[Differentiation of the palatine tonsillar tissues of the human fetus]

Differentiation of epithelial and lymphoid tissues of the palatine tonsils was studied in human embryos at the age of 8-34 weeks of development by means of histochemical, immunomorphological and morphometric methods. The anlage of the palatine tonsils appears at the age of 9 weeks of fetal development. At the age of 13-14 weeks of fetal development the tonsil suspension contains 2 subpopulations of lymphocytes possessing properties of T-cells differing in the ability of their superficial receptors to interact with sheep erythrocyte antigens forming rosettes (RFC--rosette forming cells) and with antigens of their own erithrocytes (autoRFC). The number both increases sharply by the 16th week of gestation. Simultaneously, essential alterations are noted in epithelial and lymphoid tissues. In epithelium of crypts cornified cells appear; the amount of lymphoid tissue increases sharply, primary follicles without reactive centers appear, lymphocytic infiltration of epithelium occurs. The amount of RFC does not change considerably, and the amount of autoRFC has a tendency towards some increase. From the data obtained, it is possible to suggest that human palatine tonsils already at embryonic period participate in functioning of immunogenic organs and in maintaining of immunologic homeostasis of the fetal organism.

Effect of age on immune function in terms of chemically induced cancers

Neonatal, fetal, and very old animals are particularly sensitive to chemical carcinogenesis. Reasons for this increased sensitivity could be due to increased susceptibility of "target" organs or cells, peculiar hormonal levels at these age groups, relatively deficient immune functions, or combinations of these and/or other factors. During the late fetal and first three weeks of neonatal life, the immune system is rapidly maturing, is relatively incompetent, and its diverse components are developing at different rates. For example, thymus-dependent (T) alloreactive cells capable of proliferating in mixed lymphocyte reactions (T helper cells) develop by 7 days of age, but precursors of T killer cells are not competent until approximately 14 days of age. Bursa equivalent-dependent (B) cells capable of generating antibody responses are present in fetal liver but are extremely sensitive to tolerance induction until 10-14 days of age when IgD cell surface receptors are detectable. Marrow-dependent (M) cells responsible for regulation of suppressor cells and for natural cytotoxicity to transformed tumor cells do not mature until 3 weeks of age. In very old animals, the thymus is atrophic and cell-mediated immunity is moderately suppressed. Natural cytotoxicity against tumor cells is less than normal but antibody formation (B cell function) is adequate. Gonadotrophic hormones of the pituitary or placenta are high during pregnancy, the early neonatal period, after the menopause, and in a large fraction of men over 60 years of age. These and other hormones are immunosuppressive and could theoretically facilitate carcinogenesis. The particular immune cell type, if any, responsible for resistance to chemically induced tumors has not been determined. One can only state that susceptibility to chemical carcinogenesis is associated with a relative dysfunction of the immune system and that age is an important factor.

Maternal allotype dominance and allelic exclusion in the B lineage cells of the newborn rabbit

Newborn rabbits from parents which differ at the b allotype locus (kappa chain), show a strong maternal allotype dominance, especially in the bone marrow. This concerns not only the membrane but also the cytoplasm, and it cannot be simply due to a passive uptake of maternal immunoglobulins. The spleen precedes the bone marrow for a high level of expression of the paternal allotype. In the thymus, cells which contain cytoplasmic immunoglobulin are found at low frequency, but their absolute number represent a substantial contribution to the B lineage cell pool. A small proportion of such thymus cells do not show allelic exclusion of kappa chain allotypes.

Reconstitution of T-cell function in severe combined immunodeficiency disease following transplantation of early embryonic liver cells

In a 51/2-month-old male infant with adenosine deaminase-positive severe combined immunodeficiency disease, who had no suitable bone marrow donor, immunologic reconstitution was attempted with lymphoid cells obtained from the liver of a 4- to 5-week-old-male human embryo. A mild graft-versus-host reaction began three weeks later. T-cells, which were absent prior to infusion of hepatic lymphoid cells, rose to a maximum of 554/mm3 at 16 weeks post transplantation. A normal lymphocyte response to pokeweek mitogen was not present until 25 to 30 weeks and to allogeneic cells until 39 weeks. Postive in vitro lymphocyte responses to Candida albicans were found repeatedly after 52 weeks. Twenty months following transplantation the patient is free of clinical infection, although he requires regular injections of gamma globulin.

Immunological capacity of the chicken embryo. I. Relationship between the maturation of lymphoid tissues and the occurrence of cell-mediated immunity in the developing chicken embryo

In an investigation of the ontogeny of lymphoid tissue in chick embryos to relate maturation of lymphocytes with immunological competence, the numbers and sizes of lymphocytes were determined in the thymus, bursa of Fabricius, spleen, femoral marrow and peripheral blood of embryos from the 12th to 21st day of incubation, and in 6-day-old chicks. Results showed the thymus to be the first fully developed and most active lymphocytopoietic organ, followed by the bursa. The bone marrow was not lymphocytopoietic; the spleen and bone marrow were mainly granulocytopoietic and erythropoietic; some morphological differences between thymic and bursal lymphocytes were shown by light microscopy. It appears that in embryos and young chicks the lymphocytes are derived from the thymus and bursa, but not the bone marrow. In tests of immunological competency, cells of the thymus, bursa, spleen, bone marrow and peripheral blood from 12--21-day-old embryos and 6-day-old chicks were transferred to chorioallantoic membranes of 12-day-old recipient embryos. There were distinct differences between the ability of various lymphoid tissues to induce formation of chorioallantoic pocks or splenic enlargement. The thymus, spleen and peripheral blood elicited both lymphocytic pocks and splenomegaly, the bursa elicited splenomegaly only, and the bone marrow was ineffective. The bone marrow, however, induced formation of nonlymphocytic pocks. It is concluded that the immunological activity of the chicken embryo is primarily effected by the thymus and bursa and that cell-mediated immunity appears in the 2nd week of incubation.

On the development of the lymphoid follicles of the bursa of Fabricius

The structural features of the development of the bursa of Fabricius in white Leghorn chick embryos are depicted at carefully timed intervals during embryogenesis, with emphasis on the sequence of events between the ninth and twelfth days of incubation. The direction and character of the migration of lymphoid cell precursors and granulocytes from the intravascular space to intraepithelial sites, where the formation of the primitive lymphoepithelial nodule takes place, is demonstrated. The mechanism of the mode of migration of these cells through the stromal epithelial interface is described and illustrated with electron micrographs and their role in the development of the primitive lymphoid follicles is described and discussed.