immunotoxicity (capacity and efficiency of the phagocytosis process); all of them
have shown their relevance in ERA. This strategy has been employed in the PIRENSeine programme to assess the water quality at the three pilot sites along the Seine
River following the upstream–downstream gradient: Marnay-sur-Seine, Bougival
and Triel-sur-Seine.
3.4.2 Immune Marker Response
Two sampling experiments were conducted in different hydrologic conditions: one
during the zebra mussel ‘breeding’ period between May and July 2016 and another
one during the ‘resting’ period between November and December 2016. All mussels
originated from the same population in a control site (Sainte Marie du Lac
Nuisement, lac du Der-Chantecoq, 48
36
0 22.02
00 N, 4
46
0 34.0
00 E). The day after
sampling, haemolymph was withdrawn and cellular parameters were measured.
Haemocyte distribution, cell mortality and responses relative to the phagocytosis
process were measured with flow cytometry. Using this technique, the following
data can be acquired: (1) phagocytosis capacity, defined as the percentage of cells
which have engulfed at least one bead, quantifies how many haemocytes in the entire
cell population are able to ingest beads; (2) phagocytosis efficiency, corresponding
to the percentage of cells that have engulfed at least three beads, indicates how much
phagocytic cells have efficient phagocytosis activity and are not just randomly
bound to beads; and (3) the intensity of phagocytosis activity quantified by the
haemocyte avidity, represented by the mean number of beads engulfed per cell.
During the first campaign (May–July 2016), the response of haemocyte distribution
demonstrated a site effect. In mussels caged at Triel-sur-Seine, 71% of haemocytes
showed an efficient phagocytic activity for both sampling times, whereas it was
10–20% lower for the two other sites. We did not observe this site effect during the
second campaign, but the results were time-dependent. In fact, the mean percentage
of phagocytic cells was 79% in November and 59% in December. This result was
also confirmed by another marker of phagocytic effectiveness: the avidity of
haemocytes. In November, the mean avidity of haemocytes was 10 Æ 2 beads per
cell, whereas in December, the average avidity decreased to only 6 Æ 2 beads per
cell. These results would suggest stimulated immune functions in November in
comparison with December. Globally, necrosis affected 10–28% of haemocytes
over the year. Thus, the biological endpoints measured with the flow cytometry
technique clearly show a site effect on the first campaign with the stimulation of
haemocyte functions associated with lower mortality from Marnay-sur-Seine to
Triel-sur-Seine. Full interpretation of these results is ongoing. In particular, these
results still have to be compared with environmental concentrations of contaminants
to confirm their utility as efficient biomarkers in ERA.
Experience Gained from Ecotoxicological Studies in the Seine River and. . .
257
have shown their relevance in ERA. This strategy has been employed in the PIRENSeine programme to assess the water quality at the three pilot sites along the Seine
River following the upstream–downstream gradient: Marnay-sur-Seine, Bougival
and Triel-sur-Seine.
3.4.2 Immune Marker Response
Two sampling experiments were conducted in different hydrologic conditions: one
during the zebra mussel ‘breeding’ period between May and July 2016 and another
one during the ‘resting’ period between November and December 2016. All mussels
originated from the same population in a control site (Sainte Marie du Lac
Nuisement, lac du Der-Chantecoq, 48
36
0 22.02
00 N, 4
46
0 34.0
00 E). The day after
sampling, haemolymph was withdrawn and cellular parameters were measured.
Haemocyte distribution, cell mortality and responses relative to the phagocytosis
process were measured with flow cytometry. Using this technique, the following
data can be acquired: (1) phagocytosis capacity, defined as the percentage of cells
which have engulfed at least one bead, quantifies how many haemocytes in the entire
cell population are able to ingest beads; (2) phagocytosis efficiency, corresponding
to the percentage of cells that have engulfed at least three beads, indicates how much
phagocytic cells have efficient phagocytosis activity and are not just randomly
bound to beads; and (3) the intensity of phagocytosis activity quantified by the
haemocyte avidity, represented by the mean number of beads engulfed per cell.
During the first campaign (May–July 2016), the response of haemocyte distribution
demonstrated a site effect. In mussels caged at Triel-sur-Seine, 71% of haemocytes
showed an efficient phagocytic activity for both sampling times, whereas it was
10–20% lower for the two other sites. We did not observe this site effect during the
second campaign, but the results were time-dependent. In fact, the mean percentage
of phagocytic cells was 79% in November and 59% in December. This result was
also confirmed by another marker of phagocytic effectiveness: the avidity of
haemocytes. In November, the mean avidity of haemocytes was 10 Æ 2 beads per
cell, whereas in December, the average avidity decreased to only 6 Æ 2 beads per
cell. These results would suggest stimulated immune functions in November in
comparison with December. Globally, necrosis affected 10–28% of haemocytes
over the year. Thus, the biological endpoints measured with the flow cytometry
technique clearly show a site effect on the first campaign with the stimulation of
haemocyte functions associated with lower mortality from Marnay-sur-Seine to
Triel-sur-Seine. Full interpretation of these results is ongoing. In particular, these
results still have to be compared with environmental concentrations of contaminants
to confirm their utility as efficient biomarkers in ERA.
Experience Gained from Ecotoxicological Studies in the Seine River and. . .
257