Læknablaðið : fylgirit - 01.05.1978, Qupperneq 153

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Fig. 2a Percentage of peroxidase - positive EA-
rosettes before (Ly) and after (Ly-C)
nylon fibre fractionation.
2b Cytotoxic activity of mononuclear
leukocytes from four normal blood
donors before (Ly) and after (Ly-C)
nylon fibre fractionation. Broken
horizontal lines show the mean vaiues.
obtained. After EA-rosette sedimentation the
cell suspensions remaining in the interphace were
almost completely depleted of EA-RFC, but still
retained a part of cytotoxic activity as well as
peroxidase positive cells (Table II);
Discussion:
If the Fc-receptor bearing lymphocytes (EA-
RFC) constituting the third lymphocyte population,
including the K-cells, are of monocytic origin,
they might be expected to be peroxidase positive.
The results presented in this study show that,
while about 207o of the mononuclear leukocytes
separated by the Isopaque Ficoll gradient centri-
fugation are peroxidase positive cells, the
peroxidase activity is practicaUy removed after
fractionation of the ceUs on a nylon fibre column.
On the other hand, the proportion of EA-RFC was
only slightly reduced, whUe the cytotoxic activity
against antibody coated target cells was increased
in all experiments. We have also obtained
similar results in a few preliminary experiments
where phagocytic cells were removed with a magnet
method. leading to simultaneous removal of peroxi-
dase positive ceUs, while EA-RFC were only
slightly reduced and the cytotoxic- activity was
increased (data not published).
The results indicate that the mononuclear
leukocytes which have lymphocyte morphology and
Fc-receptors as identified by their abUity to form
rosettes with ORH+ erythrocytes sensitized with
a Ripley anti-CD antiserum, do not belong to the
monocytic line, since they lack one of the most
reliable markers of monocytes, i.e. peroxidase
positivity. They are probably not immature
peroxidase negative monocytes either, because it
has been demonstrated in animals studies that the
peroxidase activily of promonocytes is much
higher than in mature monocytes, while the lowest
activity is found in activated macrophages (23).
This confirms our results where we demonstrated
that the ceUs are depleted'of peraxidase after
incubation in vitro for three days.
The data represented in this paper do not permit
any final conclusion concerning the identity and
origin of the third lymphocyte population, but do
not support the hypothesis of monocytic origin.
We have recently performed experiments with a
plaque technique to study single effector cell in
antibody and dependent cell mediated cytotoxicity
(22). This assay may give us further information
about the properties of the Fc-receptor bearing
cytotoxic effector cell. The biological functions
of the third lymphocyte population including K-
ceUs, are unknown. Whether the cytotoxic
potential of these cells contributing to the
destruction of synovial tissue in patients with
rheumatoid arthritis is unknown. However,
their presence in inflamed synovial tissue is
recently established. A small proportion of
the eluted cells has Fc-receptors as detectable
with the rosette technique (1), and also effector
ceUs inducing cytotoxicity against antibody
coated chicken orythrocytes have been demon-
strated (2).
References:
1. Abrahamsen, T.G., Fr/óland, S.S., Natvig,
J.B. and Pahle, J. Elution and characteriza-
tion of lymphocytes from rheumatoid
inflammatory tissue. Scand. J. Immunol.
4 823, 1975.
2. Abrahamsen, T.G., Fr*$land, S.S. , Natvig,
J.B. and Pahle, J. Antibody-dependent cyto-
toxicity mediated by cells eluted from synovial
tissues of patients with rheumatoid arthritis.
(Submitted for publication).
3. Aiuti, F. et al. Special Technical Reports:
Identification enumeration and isolation of B-
and T-lymphocytes from human peripheral
blood. Scand. J. Immunol. 3 521, 1974.
4. Bjóyum, A. Isolation of lymphocytes, granu-
locytes and macrophages. Scand. J. Immunol.
5 suppl. 5, 1976.
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