Retroviruses of Human A.I.D.S. and Related Animal Diseases

tion: fusion of uninfected cells to infected cells, via the interaction CD4/gpl20
at the cell surface [4], binding of free
gpl20 to CD4 lymphocyte, leading to a
cytotoxic destruction [5]. Such mechanisms are unlikely to occur at the beginning of the second phase, in which immunologic containement of the virus is
properly working.
We have recently observed in our
laboratory that lymphocytes from AIDS
patients die prematurely when cultivated
in medium devoid of interleukine 2 and
of activating agents (Fig. 3). After 3 days
of culture, lymphocytes from normal
SEPARATION OF PBLs
WASHING IN SERUM FREE MEDIUM
1
INCUBATION IN SERUM FREE MEDIUM FOR 3 DAYS
COUNTING OF DEAD CELLS EVERY DAY
Fig. 3: Protocole of the lymphocyte viability test. NB:
In recent experiments, the incubation was peiformed in
presence of 10 % fetal calf serum.
blood donors keep a good viability (less
than 10 % dead cells, as judged by
trypan blue exclusion (Fig. 4) or by
FACS analysis with acridine orange and
ethidium bromide staining). On the
contrary, lymphocyte cultures from
AIDS patients show after three days, a
high mortality in the range of 10 to 60 %
or more.
We have also observed (fig. 5) that a
fraction of living cells of these patients
14

dead cells
40
30
20
10

/
/

7.

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/ /
/

//./ /

IL
1 2 3 days 4
Fig. 4. Example of cell mortality in function of time for
the PBLs of two patients (upper curves) and of two
controls (lower curves).
have a lower nucleic acid content, at a
stage preceeding their death. When the
same test is applied to asymptomatic
carriers, those which have a normal CD4
cell number and normal CD4/CD8 ratio
behave like seronegative donors. Those
in which the CD4 cell number is decreasing have intermediate values between
normal and AIDS. Those with very low
CD4 cells behave like AIDS patients
(Fig. 6).
When the leucocyte population was
fractionated, we found that the phenomenon concerns mostly T lymphocytes
(removal of monocytes had no effect),
but CD8 + as well as CD4 + lymphocytes. Many compounds were tried to
prevent this premature death. The only
factor which restaures partially lymphocyte viability is Interleukine 2, with an
optimal dose of 10 U/ml. This effect
would suggest that Interleukine 2 acts on
some activated T cells, which needs the
growth factor to maintain their inte